Mesogenic materials with anomalous birefringence dispersion and high second order susceptibility (X(2))

ABSTRACT

This invention provides LC compositions useful as birefringent materials in electrooptic devices which exhibit zero or low negatively sloped birefringence dispersioon (e.g., exhibiting positive birefringence dispersion significantly lower than that of currently available LC compositions) or more preferably positively sloped birefringence dispersion in which birefringence of the material increases with wavelength. The invention provides compounds useful as components of LC compositions which exhibit negative birefringence where n 0  is higher than n e . The compounds of this invention are dimers of LC-like compounds in which the monomers are linked to each other through a high birefringence moiety (dimerization linker). The LC monomers consist of an LC core and one or two tail groups. Preferred monomers for this invention have low birefringence in comparison to the birefringence of the monomer linking moiety. The dimers have normal positive birefringence dispersion to have birefringence that is lower in absolute value at longer wavelengths. But since they have negative birefringence, their birefringence actually increases (i.e., goes less negative) as wavelength increases.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 08/833,280,filed Apr. 4, 1997, now U.S. Pat. No. 6,139,771, filed Apr. 4, 1997 andissued Oct. 31, 2000, and claims the benefit of provisional applicationNo. 60/015,376 filed Apr. 5, 1996, which is incorporated by reference inits entirety herein to the extent not inconsistent herewith.

This invention was made at least with partial funding from the U.S.Government through the Office of Naval Research, and the NationalScience Foundation. The United States Government may have certain rightsin this invention.

BACKGROUND OF THE INVENTION

This invention relates to compounds and liquid crystal compositionscontaining them which are useful in electooptical and non-linear opticalapplications.

Liquid crystal (LC) displays are now nearly ubiquitous in our culture,being used in both monochrome and color displays in a variety ofproducts from watches to automobile gauges and from road signs tocomputer displays. It is most desirable that monochrome displays aresimply black and white with no particular cast of color. Similarly, itis imperative for quality color displays that all colors be transmittedequally well. If a display is less transmissive for one wavelengthcompared to another, the display will not show true colors and will beless marketable than a display showing true colors.

LC displays rely on the birefringence (Δn) of the LC, i.e., thedifference in refractive indices between different orientations of theLC. Birefringence, Δn=n_(e)−n₀, where n_(e) is the index of refractionalong the extraordinary axis of a birefringent material (parallel to theoptic axis) and n₀ is the index of refraction its ordinary axis(perpendicular to the optic axis). The optimal thickness of an LC cellsuch that it behaves as a half-wave plate, to maximize contrast and truecolor transmission, at a given wavelength is proportional to thebirefringence. The optimal birefringence for a fixed pathlength, i.e.,thickness of LC, increases with increasing wavelength as shown in FIG.1. In contrast, birefringence of a given material generally decreases asa function of increasing wavelength (FIG. 1). The change inbirefringence of a material as a function of wavelength is calledbirefringence dispersion. (Herein, the term “positive birefringencedispersion” is used for birefringence that decreases with increasingwavelength and “negative birefringence dispersion” is used forbirefringence dispersion that decreases with increasing wavelength.)Thus, if birefringence of an LC cell is optimized for transmission atone wavelength by optimization of cell thickness, it will not be theoptimal birefringence at a second wavelength and as a consequence lighttransmission through the cell at the second wavelength will be lower.

Typically, in designing an LC device, a compromise is made by settingcell thickness for optimal transmission of a wavelength in the middle ofthe operational wavelength range (i.e., at the design wavelength). ForLC devices used in the visible, cell thickness is chosen to optimizetransmission of green light, giving a cell less than optimal, butuseful, transmission in the red and blue. Such a cell has a slightyellow or green cast.

If the birefringence dispersion of an LC material were negative(increasing in slope as a function of increasing wavelength), cells madefrom this material would exhibit significantly less chromatic behavior.In general, LC materials, i.e. mesogenic compositions, which exhibit alower positive (including zero) or negative birefringence dispersionthan existing materials will be useful for decreasing the chromaticbehavior of LC displays and related electrooptical devices. Suchmesogenic materials will be useful in optical filters with improvedcolor balance, larger free spectral range, maintaining high resolutionwith fewer filter stages and in tunable Fabry-Perot filters using liquidcrystal spatial light modulators (SLMs).

Furthermore, ferroelectric liquid crystals (FLCs) used in displays oftenhave quite high birefringence requiring the use of thin cells. When thinLC cells are used, small variances in cell thickness can have asignificant effect on the cell's optical properties. For example, a 0.1μm variance in thickness of a cell that is 1.1 μm thick results in a ±9%difference in transmission, while the same variance in a thicker 1.9 μmcell results in only a ±5% difference. Thinner LC cells also tend tosuffer from non-uniform spacing, which can lead to shorts. Environmentalcontamination of LC cells, for example by inclusion of dust and othercontaminants, has a more severe effect on thinner cells. Designs usingthicker cells, for more stability, easier manufacturing and lower cost,require LC materials with generally lower birefringence (compared topresently available materials). There is a general need in the art forLC materials, particularly FLC materials, with decreased birefringence.

Ferroelectric liquid crystals (FLCs) are true fluids possessingthermodynamically stable polar order. As the liquid crystal cools from anormal isotropic liquid to a crystalline state, it passes through aseries of mesogenic phases of increasing order. A typical phase sequenceincludes several phases, of which only the tilted smectic C* (S*_(c))phase possesses the thermodynamically stable polar order necessary toexhibit a net dipole moment. In the S*_(c) phase the moleculesself-assemble into layers, with the long axis of the moleculescoherently tilted with respect to the layer normal. The single polaraxis of the phase is normal to the tilt plane. For most such FLCs, aspontaneous macroscopic dipole density or spontaneous ferroelectricpolarization P along the polar axis is easily measurable.

The ferroelectric nature of a C* phase affords a very strong coupling ofthe molecular orientation with external fields, leading to a highcontrast electro-optic light valve with fast response relative to thewell known nematic devices currently in use. The complicating factor ofthe C* helix was solved with the invention of the Surface StabilizedFerroelectric Liquid Crystal (SSFLC) light valve. In the SSFLC geometry,the helix is spontaneously unwound due to surface interactions withbounding glass plates. In this case, when the director prefers aparallel orientation with respect to the surface plates, two states areallowed. In one state the molecules tilt right by tilt angle θ, while inthe other state they tilt left. In both cases, the ferroelectricpolarization vector is pointing normal to the title plane (normal to thesurface of the glass plates).

Due to the birefringence of FLC molecules, the two states have differentoptical characteristics. When the tilt angle θ=22.5°, and the thicknessof the cell is tuned correctly relative to the birefringence, then thecell behaves as a half wave plate, and can be aligned between crossedpolarizers such that one state gives good transmission, while the otherstate shows good extinction, giving rise to the desired electro-opticeffect.

SSFLC cells show very high contrast (1,500:1 demonstrated), lowswitching energy, bistability, high resolution (≡10⁷ pixels/cm²demonstrated, 10⁸ pixels/cm² possible) and other performancecharacteristics which make it particularly attractive for manyoptoelectronic applications.

Compounds which self-assemble into the smectic C phase are often termedC phase mesogens. While there is currently no detailed understanding ofthe relationship between molecular structure and the occurrence of LCphases, empirically, C phase mesogens generally possess a rigid coreseparating two “floppy” tails. The tails of chiral and achiral mesogenscan include a variety of chemical functionalities, but components ofcommercial mixtures often have one or two alkyl or alkoxy tails. Thetails often have similar lengths, and both are typically longer thanfour carbons. Many compounds of this type also exhibit a nematic phase.For C* mesogens generally one of the tails will possess one or moretetrahedral stereocenters.

In order to be useful in the many types of devices of interest, FLCmaterials must possess properties never achievable in a single compound,but the stable temperature range and other material parameters can ingeneral be tuned by mixing components. Commercial LC mixtures aregenerally composed of at least eight components. FLC mixtures generallycontain two types of components: 1) A smectic C host, designed to affordthe required temperature range and other standard LC properties; and 2)Chiral components designed to induce ferroelectric polarization andproduce fast switching or other desirable properties (e.g., tilt angleadjustment)in the FLC film. FLC mixture may also contain additionalactiral components that adjust other desirable FLC properties.

Birefringence refers to the property of a liquid crystal to interactmore strongly with light along one LC axis than along another LC axis.As discussed above, most LCs are made of a core with extensive electrondelocalization, to which one or two tails are attached to help orientthe molecules, give a dipole moment or polarization or confer otherdesirable properties on the molecule. Typical LC are rod-shaped with themajority of the pi-electron delocalization along the long orextraordinary axis (also referred to as the director). As a consequencethe extraordinary axis of LCs have the higher index of refraction, sotheir birefringence Δn=n_(e)−n₀ is positive. Birefrinence of a liquidcrystal at a given wavelength is:${{\Delta \quad n} = {{G(T)}\quad \frac{\lambda^{2}\lambda^{*^{2}}}{\lambda^{2} - \lambda^{*^{2}}}}},$

where Δn is the birefringence at a given wavelength, G is a constant, Tis the temperature, λ is the particular wavelength, λ* is the meanresonance frequency which can be calculated given the spectrum of amaterial or the its birefringence at several wavelengths. See: S.-T. W(1986) Phys. Rev. A 33:1270; S.-T. W (1987) Opt. Eng. 26:120; S.-T. W,C.-S. W (1989) J. Appl. Phys. 66:5297; S.-T. W et al. (1993) Opt. Eng.32:1775. As the wavelength of interest moves away from λ*, thebirefringence decreases asymptotically until in the infrared, thebirefrinence is relatively constant (except near IR absorbencies). Thereis, however, a large amount of birefringence dispersion in the visiblespectrum. This is particularly true if λ* is close to the visible regionso that λ²−λ^(*2) is small. When the birefringence of the typical LC ishigher at short wavelengths than at longer wavelengths, optimization ofLC cells as half-waveplates at a given wavelength generally require theopposite behavior of birefringence as a function of wavelength. FLC cellhalf-wave plates in particular require:$d = \frac{\lambda}{2\quad \Delta \quad n}$

where a wavelength (λ) of about 500 nm is usually chosen as the optimalfor LC cells (for applications in the visible). As indicated in FIG. 1,this thickness is then not optimal for all wavelengths of visible lightdue to the birefringence dispersion.

FIG. 2 shows transmission (measured and calculated) at differentwavelengths for cells with three different FLC materials (a standardmixture and two theoretical mixtures), normalized for 100% transmissionof 500 nm light. The first measured transmission (solid line) is ZLI3654 which has typical birefringence behavior with a λ* of 217 nm. Withthis mixture, only about half of the 400 nm light and about 70% of the700 nm is transmitted. A cell using this material has a noticeablegreenish cast. The second, a calculated transmission (dotted line) isthat based on use of a theoretical material in which the birefringenceis invariant with changing wavelength. A cell using such a material iscalculated to transmit about 83% of 400 nm light and about 83% of 700 nmlight. Such a cell would have much truer color, particularly in theblue, compared to the standard FLC cell. The third, another calculatedtransmission (dashed line) is that based on use of a theoreticalmaterial in which the birefringence dispersion is negative, with theabsolute value of the proportional change as a function of wavelengththe same as for the standard LC mixture. A cell using such a material iscalculated to transmit very nearly 100% of blue light and 92% of redlight, resulting in a cell with quite true colors.

The present invention relates in one aspect to low birefringencemesogens or to mesogens having anomalous birefringence dispersion. Asused herein, “anomalous” refers to birefringence dispersion atypical forliquid crystal material, either exhibiting zero (as illustrated in FIG.2 dotted line) or negative birefringence dispersion (increasing withincreasing wavelength) (as illustrated in FIG. 2 dashed line), orsignificantly less positive birefringence dispersion compared to knownLC materials. Compounds of this invention can be mesogens or can beemployed as components in mesogenic compositions to lower birefringenceor to lower birefringence dispersion.

Mesogenic materials of the present invention are chiral nonracemic andachiral materials having mesogenic phases (LC phases) useful inelectrooptical devices, including chiral and achiral tilted smecticphase materials (particularly smectic C and smectic A materials) andnematic phase materials. Mesogenic materials of this invention includethose that are ferroelectric liquid crystals (FLCs), nematic liquidcrystals, and materials useful in SSFLC, electroclinic and DHF devices.

While the discussion of anomalous birefringence dispersion herein hasfocused on FLC's used in SSFLC devices, other electrooptic devicesemploying LCs, such as nematic cells will also benefit from the use ofLC's with low or negative birefringence dispersion (and more generallyfrom LCs with low or negative birefringence). The mechanism of FLC andnematic cells differ, but in both cases optimization of cell thicknessdepends on the wavelength of light being transmitted. In nematic cellssome efforts have been made to make cells achromatic. For example, acombination of at least two polymer retarder films can be employed ascompensators to give light that is reasonably achromatic (T. Scheffer,J. Nehring (1995) SID Seminar Lecture Notes, Vol. 1, M2). However, theuse of such external means of chromaticity compensation can bedetrimental to contrast ratio or viewing angle of the device. Thus,nematic liquid crystals with little or no birefringence dispersion wouldbe quite beneficial.

Development of methods for creation of organic thin films with largeχ⁽²⁾ is a problem of great interest due to the potential utility of suchfilms in the fabrication of fast integrated electro-optic (EO)modulators. Such modulators are hybrid devices wherein the organicmaterial must work in concert with semiconductor integrated circuits.For this application the material design and synthesis task involvesthree key considerations: 1) Molecules with large molecular second ordersusceptibility χ must be created; 2) The molecules must be assembledinto a material with the correct supermolecular stereochemistry toafford the required bulk χ⁽²⁾; and 3) This material must be integratedwith a semiconductor device—a key process requiring supermolecularstereocontrol on a more global level.

Early in the development of chiral smectic FLC chemistry and physics,the spontaneous thermodynamically stable polar supermolecular structureexhibited by these anisotropic liquids suggested their potential utilityin second order nonlinear optics applications. This work, however,showed that FLCs known at the time, such as DOBAMBC, exhibited values ofχ⁽²⁾ too small to be useful (d_(eff)˜0.001 pm/V for SHG from 1064 nmlight). Efforts directed toward design of FLCs with increased χ⁽²⁾provided materials with demonstrated EO coefficients on the order of 1pm/V for modulation of 633 nm light at 100 MHz and d coefficients on theorder of 5 pm/V for SHG (Arnett et al. (1995) “Technique for MeasuringElectronic-Based Electro-Optic Coefficients for Ferroelectric LiquidCrystals” in Thin Films for Integrated Optics Applications, Wessels etal. (eds), Materials Research Society (Pittsburg, Pa.); Walba et al.(1991) Ferroelectrics 121:247; Schmitt, K. et al. (1993) Liq. Cryst.14:1735). Still, further increases in the magnitude of χ⁽²⁾ arerequired, since EO coefficients on the order of 50 pm/V are desirablefor fast integrated optics applications (Walba, D. M. (1995) Science270:250). Achieving such a large increase in χ⁽²⁾, however, seemsproblematical in FLCs since functional arrays with large molecularsusceptibility β are typically “long,” and tend to orient along thedirector when incorporated into traditional thermotropic liquid crystal(LC) structures. Since the FLC polar axis is normal to the director,small values of χ⁽²⁾ result as observed for DOBAMBC.

Achieving large χ⁽²⁾ in FLCs involves orientation of “large β”functional arrays, typically possessing two rings and a conjugatingspacer unit, along the polar axis with a high degree of supermolecularstereocontrol (Williams, D. J. (1984) Angew. Chem. Int. Ed. Engl.23:690; Quantum Chemical Computational calculations of NonlinearSusceptibilities of Organic Materials; Bredas, J. L. et al.(eds.);Special Issue of Mol. Cryst. Liq. Cryst. Sci. Technol. Sect. B, Gordon &Breach (1994) 6(3-4):135; Kanis et al. (1994) Chem. Rev. 94:195; Meyerset al. (1994) J. Am. Chem. Soc. 116:10703.) Excellent supermolecularstereocontrol is indeed achievable in FLCs (on the order of 60% polarexcess has been demonstrated as evidenced by ferroelectric polarizationmeasurements), and “large β” functional arrays are easily incorporatedinto LC structures (Kobayashi et al. (1990) Mol. Cryst. Liq. Cryst.Letts. 7:105; Fouquey et al. (1987) J. Chem. Soc. Chem. Comm. 1424;Berdague et al. (1993) Liq. Cryst. 14:667; Ikeda et al. (1993) Nature361:428; Sasaki et al (1994) J. Am. Chem. Soc. 116:625). However, in allknow cases such functional arrays orient along the liquid crystaldirector {circumflex over (n)}, while the FLC polar axis is normal tothe director.

This invention relates in a second aspect to LC compounds for NLOapplications. While an LC mesogen is not required for NLO FLCs (dopingof achiral C phase hosts with appropriate non-mesogenic quests deliversthe required supermolecular stereocontrol) mesogenicity is desirablesince for NLO applications achieving the highest possible concentrationof NLO active units is advantageous. Certain compounds of this inventionthat have negative birefringence also exhibit NLO properties. Herein wedemonstrate an approach for achieving large χ⁽²⁾ in FLCs with examplesof a class of chiral smectic materials demonstrating orientation oflarge β NLO chromophores along the polar axis.

WO 92/20058 (Walba et al.) published Nov. 12, 1992 relates toferroelectric liquid crystal materials for nonlinear opticsapplications. Certain of the compounds reported therein are monomers forthe side-by-side dimer materials of this invention. WO 92/20058 takespriority from U.S. patent application Ser. No. 07/690,633 filed Apr. 24,1991 (now abandoned). U.S. patent application Ser. No. 08/137,093, filedOct. 18, 1993, (now allowed) is the U.S. national stage application ofWO 92/20058. WO 92/20058, U.S. Ser. Nos. 07/690,633 and 08/137,093 (U.S.Pat. No. 5,543,078) are incorporated in their entirety by referenceherein.

The following U.S. patents provide general descriptions of LC's forelectrooptical applications, including FLCs: U.S. Pat. Nos. 5,051,506,5,061,814, 5,167,855, 5,178,791, 5,178,793, 5,180,520, 5,271,864,5,380,460, 5,422,037, 5,453,218, and 5,457,235. These patents areincorporated by reference in their entirety herein and provide methodsof synthesis for a variety of LC materials, including methods ofsynthesis of a variety of LC cores and chiral and achiral LC tails thatare used in the compounds of this invention. These patents also providea general description of the properties of LC materials forelectrooptical applications, particularly those for use in SSFLC,electroclinic, DHF and nematic devices.

SUMMARY OF THE INVENTION

This invention provides mesogenic compositions which exhibit anomalousdispersion. More specifically this invention provides LC compositionsuseful as birefringent materials in electrooptic devices which exhibitzero or low negatively sloped birefringence dispersion (e.g., exhibitingpositive birefringence dispersion significantly lower than that ofcurrently available LC compositions) or more preferably positivelysloped birefringence dispersion in which birefringence of the materialincreases with wavelength. As a means to this end, the inventionprovides compounds useful as components of LC compositions which exhibitnegative birefringence where n₀ is higher than n_(e). These compoundscan be doped into LC compositions having typical positive birefringencedispersion to reduce that dispersion. LC compositions with reducedbirefringence dispersion can be used to make LC cells and otherelectrooptical devices having decreased chromaticity. Preferredcompounds of this invention with negative Δn are those that mix withavailable FLC and/or nematic mixtures with minimal suppression of thedesired mesogenic phases.

Additionally, this invention provides LC electrooptic devices havingoptical retardance substantially independent of wavelength. Theinvention particularly relates to LC electrooptic devices for use in thevisible.

In a second aspect certain of the dimers of this invention have usefulNLO properties.

Most generally, the compounds of this invention are dimers of LC-likecompounds in which the monomers are linked to each other through a highbirefringence moiety (dimerization linker). The LC monomers consist ofan LC core and one or two tail groups. Preferred monomers for thisinvention have low birefringence in comparison to the birefringence ofthe monomer linking moiety. The monomers are linked to each other suchthat the relatively low birefringence groups, with little conjugation,comprise the long axis of the molecule and the high birefringencelinking moiety is substantially perpendicular to that low birefringencelong axis. This long axis preferably aligns with the director. Thesedimers, have more extensive conjugation and high birefringence along theordinary axis and as a consequence exhibit negative birefringence. Thedimers have normal positive birefringence dispersion, to havebirefringence that is lower in absolute value at longer wavelengths. Butsince they have negative birefringence, their birefringence actuallyincreases (i.e., goes less negative) as wavelength increases.

A particularly interesting subset of compounds of this invention arethose having negative birefringence and which exhibit strong absorptionbands near, but not in the visible. These materials exhibit negativebirefringence and birefringence dispersion that slopes steeply in theblue portion of the spectrum. The λ* of a material can be adjusted bychanging functional groups in the high birefringence linker betweenmonomers. Substitution with functional groups including among others,nitro groups, azo groups, Shiff bases, ketones, sulfonates, thiols, andamines can be employed to adjust absorption spectrum of the compounds ofthis invention.

When mixed into standard LC materials with positive birefringencedispersion, compounds of this invention with negative birefringenceresult in mixtures having reduced birefringence dispersion or negativebirefringence dispersion.

Compounds of this invention include those of formula I:

where

a is 0 or 1 and A is selected from the group consisting of a —C═C—,—C≡C—, —C≡C—C≡C—, —C═C—C═C—, —C≡C—C═C—C≡C—, —N═N—, —N═NO—, and a —HC═N—group;

b₁-b₄, independently of one another, are 0 or 1 and B₁-B₄, independentlyof one another, are selected from the group consisting of —C═C—, —C≡C—,—COO—, —OOC—, —CO—, —O—, —CH₂O—, —OCH₂—, —CH₂—CH₂—, —S—, —COS—, —SOC—,—CH═CHCOO—, —OOCCH═CH—, —CH═CHCOS—, and —SOCCH═CH—;

d₁ and d₂, independently of one another, are 0 or 1 and D₁ and D₂,independently of one another, are selected from the group consisting of—C═C—, —C≡C—, —COO—, —OOC—, —CO—, —O—, —CH₂O—, —OCH₂—, —CH₂—CH₂—, —S—,—COS—, —SOC—, —CH═CHCOO—, —OOCCH═CH—, —CH═CHCOS—, and —SOCCH═CH—;

e₁ and e₂, independently of one another, are 0 or 1 and E₁ and E₂,independently of one another, are selected from the group consisting of—C═C—, —C≡C—, —COO—, —OOC—, —CO—, —O—, —CH₂O—, —OCH₂—, —CH₂—CH₂—, —S—,—COS—, —SOC—, —CH═CHCOO—, —OOCCH ═CH—, —CH═CHCOS—, and —SOCCH═CH—;

six-membered aromatic rings E and F, independently of one another, arephenyl rings or phenyl rings in which one or two of the carbon atoms ofthe ring are replaced with nitrogen atoms and wherein the carbon atomsof the phenyl or nitrogen-containing phenyl rings can be substitutedwith a halogen, CN, NO₂, alkyl, alkenyl, alkynyl, haloalkyl,haloalkenyl, or haloalkynyl group (preferred halogens being fluorines);

Y₁-Y₄, substituents on rings E and F, independently of one another, areselected from the group consisting of H, halogen, CN, alkyl, alkenyl,alkynyl, haloalkyl, haloalkenyl, or haloalkynyl group (preferredhalogens being fluorines) wherein one or more non-neighboring CH₂ groupsin the substituent can be substituted with an O, or S (e.g., givingalkoxy, ether, thioether or related groups) or with a SiR^(A)R^(B)group, where R^(A) and R^(B) are small alkyl or alkenyl groups havingfrom 1 to about 6 carbon atoms, with the proviso that any ring positionof aromatic rings E or F that is a nitrogen is not substituted with anyof the Y₁-Y₄;

x and z, independently of one another are 0 or 1, and X and Z,independently of one another, are selected from the group consisting ofelectron acceptor groups, electron donor groups, H, halogen, NO₂, —C═C—,—C≡C—, —COO—, —OOC—, —CO—, O, S, —COS—, —SCO—, CN, NH, NCH₃ (moregenerally NR′, where R′ is a small alkyl having 1 to about 3 carbonatoms), NHCO, NCH₃CO (more generally NR′CO, where R′ is a small alkylhaving 1 to about 3 carbon atoms), SO, and SO₂, with the proviso thatany ring position of aromatic rings E or F that is a nitrogen is notsubstituted with any X or Z, and R⁵ and R⁶, independently of oneanother, are selected from the group consisting of H, halogen, CN,alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, or haloalkynyl group(preferred halogens being fluorines) wherein one or more non-neighboringCH₂ groups in the substituent can be substituted with an O, or S (e.g.,giving alkoxy, ether, thioether or related groups) or with aSiR^(A)R^(B) group, where R^(A) and R^(B) are small alkyl or alkenylgroups having from 1 to about 6 carbon atoms, dependent upon the X or Zgroup, R⁵ and/or R⁶ may be absent; and

M₁-M₄, independently of one another, are core moieties having from oneto four aromatic or non-aromatic rings, optionally separated by up tothree linking groups F₁-F₃ as in formula:

—[N₁]_(n1)—[F₁]_(f1)—[N₂]_(n2)—[F₂]_(f2)—[N₃]_(n3)—[F₃]_(f3)—[N₄]_(n4)—

 where

f1-f4, independently of one another, are 0 or 1, F₁-F₄, independently ofone another, are selected from the group consisting of —C═C—, —C≡C—,—COO—, —OOC—, —CO—, —O—, —CH₂O—, —OCH₂—, —CH₂—CH₂—, —S—, —COS—, —SOC—,—CH═CHCOO—, —OOCCH═CH—, —CH═CHCOS—, and —SOCCH═CH—; and

n1-n4, independently of one another, are 0 or 1, and N₁-N₄ are selectedfrom the group consisting of aromatic rings having one or two six-memberand/or five-membered aromatic rings, which may be fused or non-fusedring systems, or monocyclic or bicyclic alkyl and alkenyl non-aromaticrings having from 5 to about 12 ring carbon atoms wherein in each ringof N₁-N₄, one or more of the ring carbons can be substituted with ahalogen, CN, small alkyl, alkenyl or alkynyl group having from 1 toabout 3 carbon atoms or small halogenated alkyl, halogenated alkenyl orhalogenated alkynyl having from 1 to about 3 carbon atoms preferredhalogens being fluorines), in each ring of N₁-N₄ that is aromatic, oneor two of the ring carbons can be replaced with a nitrogen (N), in eachring of N₁-N₄ that is non-aromatic, one or two non-neighboring CH₂groups can be replaced with an oxygen; and

R¹, R², R³, and R⁴, independently of one another, are selected from thegroup consisting of linear, branched or cyclic alkyl, alkenyl or alkynylgroups having from 1 to about 20 carbon atoms wherein one or more CH₂groups can be optionally substituted with one or more halogens, or CNgroups, or in which one or more non-neighboring CH₂ groups can bereplaced with an oxygen, a sulfur, or a substituted silyl group,Si(RA)(R′), in which R^(A) and R^(B), independently, are alkyl alkenyl,alkynyl, haloalkyl, haloalkenyl or haloalkynyl groups, preferably thosehaving from 1 to about 6 carbon atoms (preferred halogens beingfluorines).

R¹, R², R³, and R⁴ groups can be chiral nonracemic groups or achiralgroups dependent upon the desired application of the compound. A subsetof R¹-R⁴ groups are fully or partially fluorinated alkyl, alkenyl oralkynyl groups, designated by R_(F). Preferred R¹-R⁴ include those thathave about 6 to about 12 carbon atoms. Preferred Y₁-Y₄ that are alkyl,alkenyl, alkynyl or halogenated derivatives thereof are those that havefrom 1 to about 6 carbon atoms. Preferred R⁵ and R⁶ that are alkyl,alkenyl, alkynyl or halogenated derivatives thereof are those havingfrom 1 to about 6 carbon atoms.

Preferred N₁-N₄ are aromatic rings having one six-member aromatic ringand monocyclic or bicyclic alkyl and alkenyl non-aromatic rings havingfrom 5 to about 12 ring carbon atoms. More preferred monocyclicnon-aromatic rings are cyclohexane and cyclohexane rings.

X and Z groups can include electron donor groups and/or electronacceptor groups as defined herein below.

In general herein, unless otherwise stated alkyl, alkenyl and alkynylgroups can contain linear, branched or cyclic portions, may be fully orpartially halogenated, one or more carbons of the group may besubstituted with halogen or CN, and one or more non-neighboring CH₂groups can be replaced with an O, S or Si(R^(A))(R^(B)), in which R^(A)and R^(B), independently, are alkyl, alkenyl, alkynyl, haloalkyl,haloalkenyl or haloalkynyl groups, preferably those having from 1 toabout 6 carbon atoms (preferred halogens being fluorines).

In the most general sense, the six member aromatic rings E and F informula I can be replace with other aromatic systems, including 5-memberaromatic rings and aromatic systems having one or two 5- or 6-memberaromatic rings, wherein the aromatic ring system can be fused ornon-fused ring system.

Compounds of this invention also include those of formula II and III:

where a, A, b₁, b₂, B₁, B₂, d₁, d₂, D₁, D₂, e₁, e₂, E₁, E₂, Y₁-Y₄, x, z.X, Z, M₁, M₂ and R¹-R⁶ are as defined for formula I;

where a, A, b₁, b₂, B₁, B₂, d₁, d₂, D₁, D₂, e₁, e₂, E₁, E₂, Y₁-Y₄, M₁,M₂ and R¹-R⁴ are as defined for formula I and;

X and Z, independently of one another except as specifically statedherein, are selected from one of the following:

(1) the group consisting of H, an electron donor or an electronacceptor, with the proviso that when one of X or Z is an electron donor,the other of X or Z is an electron acceptor; or

(2) the group consisting of H, halogen, CN, small alkyl, alkenyl oralkynyl groups having from 1 to about 3 carbon atoms, or smallhalogenated alkyl, alkenyl or alkynyl group having from 1 to about 3carbon atoms with the proviso that any ring position of aromatic rings Eor F that is a nitrogen does not carry a substituent.

R¹, R², R³ and R⁴ groups can be chiral nonracemic groups or achiralgroups dependent upon the desired application of the compound. Aparticular subset of R¹-R⁴ groups are those that are fully or partiallyfluorinated, designated by the variable R_(F).

X and Z electron donor groups include any grouping known in the art tobe an electron donor, for example any grouping causing activation of anaromatic ring relative to benzene in an electrophilic aromaticsubstitution reaction. Electron donors include groups in which the groupatom connected to the aromatic ring is less electronegative than ahalogen and where that atom possesses a lone pair able to interact withthe aromatic ring in a resonance sense. Electron donors include: OR″,NR″R′″, NR″COR′″, and OCOR″, where R″ and R′″, independently of oneanother, are H or an alkyl having from 1 to about 6 carbon atoms(preferably having from 1 to 3 carbon atoms and most preferably methyl).More preferred electron donors are NR″R′″, with N(CH₃)₂ being mostpreferred.

A particular subset of X and Z groups are those where one of X or Z isan electron donor and the other of X or Z is an electron acceptor.

X and Z electron acceptor groups include any grouping known in the artto be an electron acceptor, for example any grouping causingdeactivation of an aromatic ring relative to benzene in an electrophilicaromatic substitution reaction. Electron acceptors include, amongothers, halogens, CN, (CN)C═C(CN)₂, COR″, CO₂R″, CONR″R′″, SO₂R″, SO₂CF₃and NO₂ where R″ and R′″, independently of one another (and independentof R″ and R′″ groups of any electron donor), are H or alkyl or haloalkyl(preferably a fluoroalkyl) having from 1 to about 6 carbon atoms(preferably having 1 to 3 carbon atoms and most preferably methyl),except that in the group SOR″, R″ cannot be H. NO₂ is preferred overhalogen and CN for obtaining large molecular β. The (CN)C═C(CN)₂, SO₂CF₃and NO₂ are generally more preferred acceptors. SO₂CF₃ and NO₂ are morepreferred acceptors for ferroelectric liquid crystal materials. TheNHCOCH₃ grouping can be an acceptor if the lone pair on nitrogen isunable to interact with the aromatic ring in a resonance sense.

Compounds of this invention also include those of formula IV:

wherein a, b₁, b₂, d₁, d₂, e₁, e₂, A, B₁, B₂, D₁, D₂, E₁, E₂, Ring F,and Ring F, X, Z, Y₁-Y₄, M₁, M₂, R¹ and R² are as defined for formulaIII; and those of formula V:

wherein a, b₁, b₂, e₁, e₂, A, B₁, B₂, E₁, E₂, Ring E and Ring F, X, Z,Y₁-Y₄, M₁, M₂, R¹ and R² are as defined for foitnula II and wherein b₃,b₄, e₃, and e₄ are 0 or 1, B₃ and B₄, independently of one another andB₁ and B₂, can be the same groups as defined for B₁ and B₂, E₃ and E₄,independently of one another and E₁ and E₂, can be the same groups asdefined for E₁ and E₂, M₃ and M₄, independently of one another and M₁and M₂, can be the same groups as defined for M₁ and M₂, R³ and R⁴,independently of one another and R¹ and R², can be the same groups asdefined for R¹ and R².

In a more specific embodiment compounds of this include those of formulaVI:

wherein

c₁ and c₂, independently of one another, are 0 or 1 and C₁ and C₂,independently of one another, are selected from the group consisting of—C═C—, —C≡C—, —COO—, —OOC—, —CO—, —O—, —CH₂O—, —OCH₂—, —CH₂—CH₂—, —S—,—COS—, —SCO—, —CH═CHCOO—, —OOCCH═CH—, —CH═CHCOS— and —SOCH═CH—; and

six-membered aromatic rings G, H, I and J, independently of one another,are 1,4-phenyl rings or 1,4-phenyl rings in which one or two of thecarbon atoms of the ring are replaced with nitrogen atoms and in whichcarbons of the phenyl rings or nitrogen-containing phenyl rings can besubstituted with halogens, CN, NO₂ or small alkyl, alkenyl, alkynyl,haloalkyl, haloalkenyl or haloalkynyl groups having from 1 to about 3carbon atoms and all other variables are as defmed in formula III.

M₁ and M₂ and (M₃ and M₄) moieties of the compounds of this inventioninclude, but are not limited to those in which one or more of the N₁-N₄are

a 1,4-phenyl,

a 1,4-phenyl in which one or two of the ring carbon atoms are replacedwith nitrogens,

a 1,4-phenyl in which one or more of the carbon atoms of the ring aresubstituted with a halogen, CN, small alkyl, alkenyl or alkynyl grouphaving from 1 to about 3 carbon atoms, or small halogenated alkyl,alkenyl or alkynyl group having from 1 to about 3 carbon atoms,

a 1,4-phenyl in which one or two of the ring carbon atoms are replacedwith nitrogens and wherein one or more of the ring carbons aresubstituted with a halogen, CN group, small alkyl, alkenyl or alkynylgroup having from 1 to about 3 carbon atoms, or small halogenated alkyl,alkenyl or alkynyl group having from 1 to about 3 carbon atoms,

a 1,4-cyclohexyl or 1,4-cyclohexenyl group,

a 1,4-cyclohexyl or 1,4-cyclohexenyl group in which one or two of thenon-neighboring CH₂ groups are replaced with an oxygen,

a 1,4-cyclohexyl or 1,4-cyclohexenyl group in which one or more of thering carbons are substituted with a halogen or CN group,

a bicyclic alkyl or bicyclic alkenyl group having from 5 to about 12carbon atoms,

a bicyclic alkyl or bicyclic alkenyl group having from 5 to about 12carbon atoms in which one or two of the non-neighboring ring CH₂ groupsare replaced with an oxygen atom; and

a bicyclic alkyl or bicyclic alkenyl group having from 5 to about 12carbon atoms, in which one or more of the ring carbons are substitutedwith a halogen or CN group.

M₁ and M₂ (and M₃ and M₄) groups of this invention include those inwhich one or more of N₁-N₄ are bicyclic [2,2,n] alkyl or alkenyl ringgroups comprising a cyclohexyl or cyclohexenyl ring where n is aninteger from 1 to about 6 wherein the bicyclic ring is optionallysubstituted with one or more halogens or CN groups.

Compounds of this invention also include those in which M₁, M₂, M₃, andM₄ are 1,4-cyclohexyl or 1,4-cyclohexenyl group, particularly those inwhich the cyclohexyl or cyclohexenyl group is in the transconfiguration.

“A” groups are conjugating linker groups between the LC monomers. When ais 0 in formulas I-VI, then there is a single bond linking the rings ofthe dimerization link, preferred dimerization linkers when a is 0 arethose containing at least one aromatic ring, such as biphenyl groups,phenylpyridine groups or phenylpyrimidine groups. Preferred “A” groupsare —C≡C—, trans —C═C—, —C≡C—C≡C— and —N═N—.

Preferred for NLO applications are compounds of this invention offormulas I-VI in which X is an electron donor or acceptor and Z is anelectron acceptor or donor. More preferred electron acceptors are —NH₂and N(CH₃)₂. Preferred electron donors are CN or NO₂.

Preferred achiral tails are those in which E₁-E₄ are O or S or those inwhich e₁-e₄ are 0.

In general, any chiral nonracemic LC tail group that is known to beuseful in the preparation of FLC's or FLC dopant materials can beemployed as a chiral tail group in the compounds of this invention. U.S.Pat. Nos. 5,051,506, 5,061,814, 5,167,855, 5,178,791, 5,178,793,5,180,520, 5,271,864, 5,380,460, 5,422,037, 5,453,218, and 5,457,235,provide exemplary chiral (as well as achiral) tail groups for FLC, DHFand nematic LCs. Specifically, chiral tails of this invention includechiral 1-methylalkoxy groups, chiral 2,3-dihaloalkoxy groups, chiral2-halo-3-methyl alkoxy and ester tails.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 Graph of birefringence versus wavelength for a fixed-thickness LCcell.

FIG. 2 Graph of percent transmission versus wavelength for cells ofthree different FLC materials.

FIG. 3 Phase diagram of compound 84 in host compound W314.

FIG. 4 Graph of ferroelectric polarization versus percent mixture forcompound 84.

FIG. 5 Graph of birefringence versus wavelength for compound MDW 1069 inthe visible regions.

DETAILED DESCRIPTION OF THE INVENTION

In one aspect, the compounds of this invention are made up oflow-birefringence monomers that are linked together to form dimers. Thebirefringence of the monomers is preferably minimized while making themcompatible with the smectic C, nematic or other mesogenic phases. At thesame time a highly birefringent group is incorporated perpendicular tothe monomer's long axis. This moiety is the dimerization link. Severaltypes of moieties typically used as cores in LC molecules are listedwith their approximate birefringence in Scheme 1:

Scheme 1 approx. approx. Δn Δn 0.12

0.22

0.14

0.23

0.19

0.31

0.21

0.33

Incorporation of moieties like those in Scheme 1, with birefringencehigher than about 0.12 as the dimerization link perpendicular to themolecule's long axis ensures that n₀ will be greater than n_(e) and thatthe dimer will have negative birefringence. U.S. patent application Ser.No. 08/301,121 filed Sep. 9, 1994 (U.S. Pat. No. 5,626,792) and Ser. No.08/458,411 (now abandoned) filed Jun. 2, 1995 disclose compounds havinghigh birefringence LC cores suitable for use as dimerization links inthe compounds of this invention. These pending U.S. patent applicationsare incorporated in their entirety by reference herein.

Phenylbenzoate moieties have birefringence generally too low for use asdimerization links in the compounds of this invention. In contrast, abiphenyl moiety having birefringence of about 1.3 is useful as adimerization link. Note that one type of exemplary dimerization link iscomposed of two Ph groups (where Ph is a 1,4-phenyl, or a 1,4-phenyl inwhich one or two ring carbons are replaced with nitrogen, for example,pyrimidinyl or pyridinyl) joined by a conjugating linking group A, forexample: C≡C or C≡C—C≡C and other groups listed above, as in the moiety:—Ph—A—Ph—. In some cases the conjugation of the dimerization link isextended on one side of the Ph's as in the general formula: —A′—Ph—A—Ph—or —Ph—A—Ph—A′, where A′ can be the same conjugating groups as A. Usefuldimerization links also include those in which conjugation is extendedon both sides of the Ph's, as in the formula: —A′—Ph—A—Ph—A′—. The Phrings of the dimerization link represent a portion of the core of the LCmonomer. Substitution on the Ph rings of the dimerization link can beused to adjust the absorption spectra of the diners to give a desiredoptimal birefringence dispersion.

The LC monomers that represent the lower birefringence and substantiallylinear moiety composing the long axis of the dimers of this inventioncan be generally represented by the formula:

R—D—Ph—B—M—E—R′

where Ph—B—M represents the core of the LC moiety, R and R′ are chiralor achiral tail groups and D and E are optional linking groups betweenthe core and the tails. B is an optional linking group between M and thePh group and M can be a generally linear array of up to about fouraromatic and/or alicyclic rings (N's) optionally separated by linkinggroups (F's):

—N—F—N′—F′—N″—F″—N′″—.

N ring groups of the monomers can be substituted with a variety ofgroups to adjust properties of the monomer (and dimers) for example toadjust LC properties or introduce NLO properties (as discussed below).

Monomers can be linked together at the Ph groups to form dimers inseveral configurations including a head-to-head (HH) and head-to-tail(HT) configurations, illustrated as:

Compounds 2 and 3 are examples of head-to-tail configurations andcompounds 4 and 5 are examples of head-to-head configurations.

More generally, the dimerization link can be mediated by any aromatic oralicyclic ring, in which alicyclic rings include, among others,cyclohexane and cyclohexene rings and bicyclic rings, such as-Cyc-A-Cyc-, where A is a conjugated linker as listed above in thedefinition of A, such as —C≡C— or —C≡C—C≡C— and Cyc=an alicyclic ringincluding a cyclohexane or cyclohexene ring. In this case too,conjugation can be extended on either side of the alicyclic rings as inthe formulas; —A′-Cyc-A-Cyc-, -Cyc-A-Cyc-A′— or —A′-Cyc-A-Cyc-A′—. Ifthe dimerization link is made through an alicyclic ring then the monomerneed not contain any aromatic rings. Monomers in such cases can be givenby the formula:

R—D-Cyc-B—M—E—R′

where variables are as defined in the previous section. Dimers linkedthrough dimerization links having alicyclic rings can be linked inhead-to-tail HT and head-to-head HH configurations as described above.

Again more generally, the dimerization link between low birefringencemonomers can be between any ring on one monomer and any ring on theother monomer. Note that although the term dimer has been used, thecompounds of this invention include those “dimers” combining twostructurally different monomers. Thus, the Ph or Cyc ring of thedimerization link need not be a terminal ring of the core linked to oneof the tail groups, as illustrated by the monomer formulas:

R—D—M—B—Ph—B′—M′—E—R′

R—D—M—B-Cyc-B′—M′—E—R′

where M′ and B′ can be selected from the same groups as M and B and thedimers are illustrated in formulas:

Compound 1 is an example of a dimer of this invention in which thedimerization link is between internal rings of the monomer core.

In general, the more rings a compound has, the more likely the compoundwill have mesogenic phases, although compounds with four or more ringstend to have higher viscosity and tend to be less soluble. Monomer corescan be extended without significantly increasing the birefringence alongthe long axis by including alicyclic rings, such as cyclohexyl andbicyclic rings, in the M core. These rings are linked in the monomercore in a generally linear fashion. Exemplary alicyclic M groups (withexemplary R shown) include:

M core N rings can be one and two ring aromatics, such as 1,4-phenyl,2,5-pyridinyl, 2,5-pyrimidinyl, napthalenyl, and biphenyl or alicyclicrings, such as trans-cyclohexyl, trans-cyclohexenyl,1,4-bicyclo[2,2,2]octyl, and 1,4-bicyclo[2,2,2]octenyl. Bicyclic ringssuitable for use as monomer N groups include those having from 5 toabout 12 carbons in the bicyclic ring and include those bicyclic ringshaving 2 six-member rings ([2,2,2] rings), one six-member ring ([2,2,n]rings, where n is 1 about 6), and propellanes ([1,1,1] rings). Alicyclicand aromatic rings of the M groups can be substituted with a variety offunctional groups including halogens (particularly fluorines), CN orNO₂.

R and R′ groups are also generally linear and can contain a variety offunctionalities. R and R′ can be chiral non-racemic or achiral.Exemplary R and R′ tail groups include the following:

R— R—≡— A. alkyl- B. alkyl—≡— CH₃—Si(CH₃)₂—(CH₂)_(n)CH₃—Si(CH₃)₂—(CH₂)_(n)—≡— CH₃—(CH₂)_(n)—═—(CH₂)_(m)—CH₃—(CH₂)_(n)—═—(CH₂)_(m)—≡— CH₂═CH₂—(CH₂)_(n)— CH₂═CH₂—(CH₂)_(n)—≡—CH₃—(CH₂)_(n)—≡—(CH₂)_(m)— CH₃—(CH₂)_(n)—≡—(CH₂)_(m)—≡—CH₃—(CH₂)_(n)—O—(CH₂)_(m)— CH₃—(CH₂)_(n)—O—(CH₂)_(m)—≡—CH₃—(CH₂)_(n)—S—(CH₂)_(m)— CH₃—(CH₂)_(n)—S—(CH₂)_(m)—≡—CH₃—(CH₂)_(n)—CF₂—(CH₂)_(m)— CH₃—(CH₂)_(n)—CF₂—(CH₂)_(m)—≡—CF₃—(CH₂)_(n)— CF₃—(CH₂)_(n)—≡— CF₃CF₂—(CH₂)_(n)— CF₃CF₂—(CH₂)_(n)—≡—CF₃—(CF₂)_(n)—(CH₂)_(m)— CF₃—(CF₂)_(n)—(CH₂)_(m)— c-propyl-(CH₂)_(n−3)—All other R₁ from column A c-hexyl-(CH₂)_(n−6) R—═— R—O— C. alkyl—═— D.alkoxy- CH₃—Si(CH₃)₂—(CH₂)_(n)—═— CH₃—Si(CH₃)₂—(CH₂)_(n)—O—CH₃—(CH₂)_(n)—═—(CH₂)_(m)—═— CH₃—(CH₂)_(n)—═—(CH₂)_(m)—O—CH₂═CH₂—(CH₂)_(n)—═— CH₂═CH₂—(CH₂)_(n)—O— CH₃—(CH₂)_(n)—≡—(CH₂)_(m)—═—CH₃—(CH₂)_(n)—≡—(CH₂)_(m)—O— CH₃—(CH₂)_(n)—O—(CH₂)_(m)—═—CH₃—(CH₂)_(n)—O—(CH₂)_(m)—O— CH₃—(CH₂)_(n)—S—(CH₂)_(m)—═—CH₃—(CH₂)_(n)—S—(CH₂)_(m)—O— CH₃—(CH₂)_(n)—CF₂—(CH₂)_(m)—═—CH₃—(CH₂)_(n)—CF₂—(CH₂)_(m)—O— CF₃—(CH₂)_(n)—═— CF₃—(CH₂)_(n)—O—CF₃CF₂—(CH₂)_(n)—═— CF₃CF₂—(CH₂)_(n)—O— CH₃(CH₂)_(n)—O—CO—═— All other Rfrom column A CH₃(CH₂)_(n)—S—CO—═— All other P from column A R₁—S— E.CH₃—Si(CH₃)₂—(CH₂)_(n)—S— CH₃—(CH₂)_(n)—═—(CH₂)_(m)—S—CH₂═CH₂—(CH₂)_(n)—S— CH₃—(CH₂)_(n)—≡—(CH₂)_(m)—S—CH₃—(CH₂)_(n)—O—(CH₂)_(m)—S— CH₃—(CH₂)_(n)—S—(CH₂)_(m)—S—CH₃—(CH₂)_(n)—CF₂—(CH₂)_(m)—S— CF₃—(CH₂)_(n)—S— CF₃CF₂—(CH₂)_(n)—S— Allother R₁ from column A

All other R₁ from column A

where n and m are integers; n+m less than or equal to about 20; Z is asingle bond, oxygen or sulfur; M is —CH₂—, a single bond or oxygen and ais 0 or 1.

CH₃—Si(CH₃)₂—(CH₂)n—

CH₃—(CH₂)_(n)—═—(CH₂)_(m)—

CH₂═CH₂—(CH₂)_(n)—

CH₃—(CH₂)_(n—≡—(CH) ₂)_(m)—

CH₃—(CH₂)_(n)—O—(CH₂)_(m)—

CH₃—(CH₂)_(n)—S—(CH₂)_(m)—

CH₃—(CH₂)_(n)—CF₂—(CH₂)_(m)—

CF₃—(CH₂)_(n)—

CF₃CF₂—(CH₂)_(n)—

CF₃—(CF₂)_(n)—(CH₂)_(m)—

CH₃—(CF₂)_(n)—(CH₂)_(m)—

n and m are integers; n+m less than or equal to about 20.

Exemplary R_(F)—X—

R_(F)— R_(F)—O— CH₃—(CH₂)_(n)—CF₂—(CH₂)_(m)—CH₃—(CH₂)_(n)—CF₂—(CH₂)_(m)—O— where: n + m ≦ about 18 or n + 1 = m andn + m ≦ about 18 CH₃—(CH₂)_(n)—(CF₂)_(m)— CH₃—(CH₂)_(n)—(CF₂)_(m)—O—where: n + m ≦ about 19 n + 1 = m and n + m ≦ about 19 CF₃—(CH₂)_(n)—CF₃—(CH₂)_(n)—O— where: n ≦ about 19 CF₃CF₂—(CH₂)_(n)—CF₃CF₂—(CH₂)_(n)—O— where: n ≦ about 18 CF₃—(CF₂)_(n)—(CH₂)_(m)—CF₃—(CF₂)_(n)—(CH₂)_(m)—O— where: n + m ≦ about 19 or n + 1 = m and n +m ≦ about 19 CH₂═CH—(CF₂)_(n)— CH₂═CH—(CF₂)_(n)—O— where: n ≦ about 18CF₂═CF—(CF₂)_(n)— CF₂═CF—(CF₂)_(n)—O— where: n ≦ about 18CF₃—(CF₂)_(n)—CH═CH—(CH₂)_(m)— CF₃—(CF₂)_(n)—CH═CH—(CH₂)_(m)—O— where:n + m ≦ 17 or n + 1 = m and n + m ≦ 17 CF₃—(CF₂)_(n)—(CH₂)_(m)—CH═CH—where: n + m ≦ 17 or n + 2 = m and n + m ≦ 17 c-propyl-(CF₂)_(n)—c-propyl-(CF₂)_(n)—O— where: n ≦ about 17 CF₃—(CF₂)_(n)—CF₃—(CF₂)_(n)—O— where: n ≦ about 19 CF₂H—(CF₂)_(n)— CF₂H—(CF₂)_(n)—O—where: n ≦ about 19 CF₂H—(CF₂)_(n)—(CH₂)_(m)—CF₂H—(CF₂)_(n)—(CH₂)_(m)—O— where: n + m ≦ about 19 or n + 1 = m and n +m ≦ about 19 Note: n and m are both integers

CH₃—(CH₂)_(n)—

Branched alkyl-

CH₃—Si(CH₃)₂—(CH₂)n—

CH₃—(CH₂)_(n)—CH═CH—(CH₂)_(m)—

CH₂═CH₂—(CH₂)_(n)—

CH₃—(CH₂)_(n)—C≡C—(CH₂)_(m)—

CH₃—(CH₂)_(n)—O—(CH₂)_(m)—

CH₃—(CH₂)_(n)—S—(CH₂)_(m)—

CH₃—(CH₂)_(n)—CF₂—(CH₂)_(m)—

CF₃—(CH₂)_(n)—

CF₃CF₂—(CH₂)_(n)—

CF₃—(CF₂)_(n)—(CH₂)_(m)—

CH₃—(CF₂)_(n)—(CH₂)_(m)—

CF₃—(CF₂)_(n)—

c-cyclopropyl-(CH₂)_(n)—

c-hexyl-(CH₂)_(n)—

where: n and m are integers; n+m≦about 20.

Specific types of compounds of this invention include those listed inSchemes 2-7:

Scheme 4

Core Tails

Compound R₁ R₂ R₃ 83 C₈ C₈ C₁₀ 84 C₈ C₈ LA 85 C₇ C₈ LA 86 C₈ C₇ LA

Methods of synthesis for several types of compounds of this inventionare exemplified in the Examples section, including several reactionschemes, below. One of ordinary skill in the art can use the exemplifiedmethods, or routine adaptations or modifications of these methods and incombination with methods well known in the art can synthesize any of thedimer compounds of this invention.

Compounds of this invention are useful as components in LC compositionshaving reduced or negative birefringence dispersion (compared to typicalLC compositions composed of monomer LC compounds). Mesogenic compositionof this invention include those that incorporate one or more of thedimers of this invention. Typically an LC composition can contain fromabout 1% to about 50% of a dimer (or a mixture of dimers of thisinvention). The amount of negative birefringent dimer or dimers includedin a given composition is adjusted to maximize benefit to thebirefringence dispersion without significant detriment to desiredmesogenic (LC) properties.

The LC compositions of this invention with anomalous dispersion areuseful in a variety of electrooptical devices to reduce chromaticity.Device applications include, among others, FLC-, nematic-, and DHF-basedoptical cells and devices, small area displays, nematic displays,Fabry-Perot tunable filters, optical bandwidth filters, and polarizationfilters.

In a second aspect this invention relates to LC materials having NLOproperties. While excellent improvement of χ⁽²⁾ in FLCs has beenachieved by design, useful materials for integrated optics clearlyrequire further increases in susceptibility. Thus, a value for theelectro-optic coefficient of 50 pm/V for modulation of 1.3 μm light atfrequencies on the order of 50 GHz seems a reasonable target, and indeedeven larger EO coefficients would be highly desirable. Prototypical“large β” functional arrays, typified by the Disperse Red 1 (DR1)chromophore (β=49×10⁻³⁰ esu), involve at least two rings linked by aconjugating spacer unit. While such units are easily incorporated intoLC structures, in all known cases such functional arrays orient alongthe liquid crystal director, while in C*FLCs the polar axis is normal tothe director. Maintaining the LC aspect ratio of an LC compound with atwo ring β unit, such as that present in DR1, oriented normal to thedirector would require such a long structure that an intractablematerial would be expected. Thus the aspect ratio argument seems topreclude the orientation of large β units along the polar axis in FLCs,limiting the obtainable χ⁽²⁾ values.

Initial results of a study directed towards developing a solution tothis problem are illustrated below:

A side-by-side dimer structure such as 70 would show the followingdesired properties: 1) Dimers such as 70 show considerable solubility inC phase hosts; 2) The tolan and biphenyl units orient along thedirector, forcing the DR1 chromophore to make a large angle to thedirector; and 3) Steric coupling of the chiral tails with the orthosubstituents provides polar orientation of the DR1 unit in the FLCphase, as required for χ⁽²⁾.

The azo dye 70 mixes up to at least 30% by weight in the C phase hostracemic 73a, with the 30% mixture showing a 20° enantiotropic C* phaserange and a very broad monotropic C* phase. The sign of the observedferroelectric polarization for (S,S)-70 (opposite that observed for(S)-73a is consistent with the expected supermolecular structure sincethe dipole contribution from the azo unit should be opposed to dipolecontributions from the ether oxygens, and of larger magnitude. Finally,preliminary visible light spectroscopy measurements show thatparallel-aligned samples exhibit the expected negative dichroism(dichroic ratio <1) suggesting that the axo unit is making an angle >54°(the magic angle) with the LC director. The value ofP_(ext)≈0.5D/molecule (assuming a density of 1.1 gms/cm³ for themixture) suggests a polar excess of ≈10% assuming a net dipole normal tothe director of 5D.

That the polar excess obtained with compound 70 is smaller than thatobtained for the o-nitroalkoxyphenyl systems 73 and 76 is likely not dueto the dimer structure itself, but rather to the relatively weak polarorientation of aryl rings observed when a dimethylamino grouping isplaced ortho to the 1-methylheptyloxy chiral tail. Thus, thebiphenylbenzoate 78 exhibits a very small extrapolated polarization (5nC/cm², sign not given), while as noted above, in racemic 73a as hostthe “flipped” o-nitroalkoxyaniline induces a very large negativepolarization in mixtures.

The “side-by-side” LC dimer 70 exhibited relatively low ferroelectricpolarizations (P≈+60 nC/cm²), and small polar excesses (pe≈15%). Weconsidered that the dimethylamino unit could exhibit poor stericcoupling with the chiral tail.

We examined the steric control that the chiral tails exert on the DR1chromophore in order to orient it along the polar axis. Substitution ofthe methyl group on the chiral tail for a hydrogen should eliminate anysteric bias between the two conformations. Thus, the polarization dropsto zero (it must since the system becomes achiral). For the azo systemthere are two chiral tails. These tails sterically couple with thedimethylamino and the trans-azo moieties. The “mono chiral tailed”analogs 85 and 86 yielded 60% and 20% lower values for P respectively,than compound 84 with two chiral tails. Thus, each tail-core systemcontributes to the overall orientation of the DRI unit (thedimethylamino moiety appears to be twice as effective as the trans-azolinkage), however, in all cases the polar order is quite low, withpe≈13% for compounds 83 and 84.

Scheme 10 Core Tails

P @ ° C. Compound R₁ R₂ R₃ Phase Diagram (nC/cm²) P_(ext)/sin(θ) pe 83C₈ C₈ C₁₀

+35.6 @ 50^(a) 129 13% 84 C₈ C₈ LA

+33.1 @ 55^(a) 133 13% 85 C₇ C₈ LA

 +8.7 @ 55^(b)  55  4% 86 C₈ C₇ LA

+20.0 @ 45^(b) +32.3 @ 85^(c) 107 204 10% ^(a)50% by weight in racemicW314. ^(b)40% by weight in racemic W314. ^(c)Neat

Compound 84 is miscible in all proportions with host racemic W314 withmixtures exhibiting a C* phase up to 60% by weight as shown by thefollowing phase diagram in FIG. 3. The ferroelectric polarization ofthese C* mixtures is well-behaved, as indicated in the following plot inFIG. 4. These figures show an extrapolated polarization of +65 nC/cm²(about 0.4 D/molecule) for 84.

One possible explanation for the poor stereocontrol exhibited by theo-dimethylamino system is suggested by MOPAC semi-empirical quantummechanics calculations using the AM1 Hamiltonian. The so-called “anisoleeffect,” whereby the aromatic ring and the alkoxy bond lie in the sameplane, is an important contributor to the overall steric coupling of oursystems. The following diagram illustrates this problem with twopossible conformations for the alkoxy bond relative to the aryl ring.Calculations suggests that conformation B is preferred over A when thedimethylamino group is situated ortho to the alkoxy tail. This wouldlead to poor steric coupling:

Since dimethylaminonitrostilbene (DANS) is known to possess a larger βvalue than DR1, the carbon analogs 93 and 94 of the azo dyes weresynthesized. Compound 93 shows excellent mesogenicity with enantiotropicN* and A* phases. The DANS dimer 94 is not mesogenic. Characterizationof 94 in a mixture with racemic W314:

suggests that the supermolecular structure obtained with the DANS dimeris similar to that obtained in the DR1 case, with a 10% polar excess fororientation of the chromophore indicated by the observed ferroelectricpolarization.

In dimers of this invention for NLO applications, substituted at X and Zpositions (see Formulas I-IV), compounds in which the electron donor issubstituted ortho to the chiral tail are preferred having generallyhigher ferroelectric polarization compared to the analogous compoundshaving the electron donor in the meta position with respect to thechiral tail. This improvement is illustrated by the followingcomparison:

EXAMPLES

Exemplary Syntheses of Negative Birefringence Dimers

Example 1.1

Compound 2 can be made according to the method outlined in the followingScheme:

The Synthesis of Tolane and Styrene Compounds

Cyclohexylethylenephenol 6 can be brominated using elemental bromine inacetic acid, giving a bromophenol. The phenol moiety can then beprotected as the tetrahydropyran using dihydropyran with an acidcatalyst, resulting in the THP ether 7. This material can then betransformed into an alkyne using trimethylsilylacetylene and a palladiumcatalyst (D. Dawson et al. (1987) “Polymers for High TechnologyElectronics and Photonics”:445.) The trimethylsilyl group can then beremoved using potassium carbonate in methanol, resulting in theacetylene 8. This, in turn, can be treated with another equivalent ofaryl bromide 7 to give a tolane. The THP groups can be removed from thetolane using methanol with catalytic acid to give the dephenol. A secondtail can then be attached, either by adding an acid chloride in thepresence of triethylamine to give an ester, or by using an alkyl halidein the presence of cesium carbonate to give an ether. In either event,the result will be a compound of type 2.

Tolane 2 can then be partially reduced to give the styrene 3. Since thetrans configuration of the double bond is desired, the preferentialreduction path is using lithium in liquid ammonia. These reactionconditions are not used if compound 2 is an ester. However, in that casethe lithium reaction can be done before the THP groups are removed.

Example 1.2

The synthesis of the alkynyltolane 4 is detailed in the followingScheme:

The Synthesis of Alkynyltolanes

The starting materials are chlorohydroquinone 9, which is commerciallyavailable, and tosylate 10. Combining the two in dimethylformamide andtreating the mixture with sodium hydride gives a statistical mixture ofthe 3-chlorophenol 11 and the 2-chlorophenol 13. Chlorophenol 11 canthen be brominated with elemental bromine in acetic acid to give themonobromide. The bromination selectively takes place at the leasthindered position, para to the chlorine. Protection of the alcohol withdihydropyran will give the THP ether 12. Chlorophenol 13 can first betreated with triisopropylsilyl triflate to give the protected phenol,then alkynated with trimethylsilylacetylene, and the TMS group removedwith potassium carbonate to give the acetylene 14.

Trimethylsilylacetylene should selectively react with the bromine ofcompound 12 to give the protected monoalkyne. This compound can then becoupled with acetylene 14 to give the alkynyltolane 15.Tetrabutylammonium fluoride removes both the TMS group from theacetylene and the TIPS group from the phenol. One tail can then beattached to the deprotected phenol. The THP group can then be removedwith acid, and another tail attached to the other phenol to give product4. Note that, using this system of protecting groups, it is possible toplace different tails on the two phenols, thus making the compound lesssymmetrical and allowing greater versatility.

Example 1.3

Diacetylene materials are relatively unstable to UV light. However, whena cinnamate group is substituted onto placed on the material, theybecome remarkably stable to UV light. We believe that this remarkablestability is due to a pathway for the non-destructive release of theenergy absorbed, namely cis-trans isomerization of the cinnamate doublebond. This probably proceeds through a twist-state biradical,suppressing other undesired pathways that would result in decomposition.Due to binding site forces, this intermediate will be somewhat morelikely to return to the trans form of the cinnamate upon recombinationof the biradical. Thus, the synthesis of the more UV-stable diacetylenecinnamate is provided in the following Scheme:

The starting material for the diacetylene cinnamate ishydroxybenzaldehyde 16. Bromination with elemental bromine in aceticacid gives the monobromide, which can be alkylated using the cyclohexyltosylate 10. The aryl bromide is alkynated with trimethylsilylacetyleneand the product deprotected with potassium carbonate. The cinnamategroup can be introduced by a Wittig reaction using acarboalkoxytriphenylphosphorane, which can be made using any desiredalkoxy group. Since this will be a stabilized Wittig reaction, it willpreferentially give the trans alkene 17. The alkyne of 17 can be coupledwith the alkyne of compound 14, giving the diacetylene. Finally, thephenol can be deprotected using tetrabutylammonium fluoride, thencoupled with an alkyl halide to give the desired product 5. Again, thetails used in the two monomeric portions of the molecule can be the sameor different, allowing a great deal of versatility.

In several of the foregoing synthetic schemes, the cyclohexylmethylenegroup is used to etherify a phenol near the onset of the synthesis.Other cyclcohexy groups, including bicyclic groups with 6-membered ringswhich should serve equally well in this step.

Example 1.4

Instrumentation and General Procedures

Melting points and first order phase transitions were measured bydifferential scanning calorimetry on a Mettler (model-E) DSC. The phasediagrams were also determined by optical microscopy with a Meiji LabaxCO, LTD.[Japan](model mK1) temperature controller. Thin layerchromatography was performed on pre-coated sheets gel 60 F₂₅₄ (layerthickness 0.2 mm).

Polarization measurements were made using ITO coated cells that weretypically 2.8μ thick and were capillary filled with the mesogen in theisotropic state. Alignment layers were obtained by dipping the cellplates in a 0.5% methanolic solution of DuPont Elvamide followed byanti-parallel rubbing with a sable paint brush.

Most solvents were used as supplied by the vendor. Dry tetrahydrofuranwas obtained by distillation from sodium. Anhydrous diethyl ether wasused as supplied by the vendor. All starting materials were obtainedfrom commercial sources unless otherwise noted.

Example 1.5

Unsaturated Alcohols

General synthesis of the alcohols. A typical procedure for the synthesisof the fatty acid derived alcohols is described. Linoleic acid (3.5 g,12.48 mmol) dissolved in 20 ml anhydrous ether was added dropwise at 0°C. and under argon, to a suspension of LAH (947 mg, 24.9 mmol) in 280 mlanhydrous ether. The reaction mixture was stirred at 25° C. for 5 hoursand was then carefully quenched at 0° C. with 5% HCl. The organic layerwas separated, washed with brine, and dried over MgSO₄. Evaporation ofsolvent yielded 3.193 g (96%) of a colorless liquid. Exemplary alcohols26a-j prepared as starting materials for synthesis of compounds of thisinvention are given in Table 1.

TABLE 1 Exemplary Synthesis of Alcohols from Commercially AvailableFatty Acids, Aldehydes, and Carboxylic Acids.

26 a R = C₁₈H₃₇— 26 g

b

h

c

i

d

j

e

f

1-Octadecanal (26a). This material is commercially available fromAldrich Chemicals.

cis-9-Octadecanol (26b). This material is commercially available fromAldrich Chemicals.

cis-9, cis-12-Octadecadienol (26c) (Linoleic acid). This material iscommercially available.

trans-9, trans-12-Octadecadienol (26d) This material was obtained fromSigma Chemicals. The crude material was purified via flashchromatography over silica gel 80/20 (v/v) (Hex/EtOAc).

cis-9, cis-12, cis-15-Octadecatrienol (26e) (Linolenic acid). Thismaterial was obtained from Sigma Chemicals.

cis-6, cis-9, cis-12-Octadecatrienol (26f) (γ-Linolenic acid). Thismaterial was obtained from Sigma Chemicals.

trans-2-Decenol (26g). This material was purchased from LancasterChemicals.

trans-3-Decenol (26h). The precursor carboxylic acid was obtained fromLancaster Chemicals. The carboxylic acid (3.0 g, 17.6 mmol), and LAH(1.337 mg, 35.2 mmol) in 300 ml anhydrous ether were reacted accordingto the general procedure. The crude alcohol was purified via flashchromatography over silica gel with gradual elutions from 98/2-50/50(v/v %) (Hex/EtOAc). Evaporation of solvent yielded 2.32 g (84%) of acolorless oil. This was only 98% pure by NMR andwas used without furtherpurification.

trans-4Decenol (26i). The precursor aldehyde was obtained from LancasterChemicals. The aldehyde (2.0 g, 12.96 mmol), and LAH (984 mg, 25.9 mmol)in 200 ml anhydrous ether were reacted according to the generalprocedure. The crude alcohol was purified via flash chromatography oversilica gel with gradual elutions from 90/10-50/50 (v/v %) (Hex/EtOAc).This was used without further purification.

trans-5-Decenol (26j). This material was purchased from AldrichChemicals.

Cyanobiphenyls

Synthesis of Alkoxycyanobiphenyls

4′-(Octadecyloxy)-4-cyanobiphenyl(W400) (Hughes, D. L., “The MitsunobuReaction” in Organic Reactions: Paquette, L. A., et al., Eds., JohnWiley & Sons, Inc. (1992) 42:335-656). To a suspension of4′-hydroxy-4-biphenylcarbonitrile (Aldrich) (200 mg, 1.0 mmol),1-octadecanol 26a (291 mg, 1.07 mmol), and triphenylphosphine (TPP) (336mg, 1.3 mmol) in 10 ml anhydrous ether, was addeddiethylazodicarboxylate (DEAD) (223 mg, 1.3 mmol) via syringe withstirring and under argon. The reaction mixture was stirred for 7 hoursunder argon at 25 ° C., and was then adsorbed onto silica gel. The crudeproduct was purified via flash chromatography with gradual elutions from98/2 to 80/20 (v/v) (Hex/EtOAc). Evaporation of the solvent, andrecrystallization from hexane yielded 322 mg (70%) of a white solid.

4′-(cis-9-Octadecenyloxy)-4-cyanobiphenyl (W396). To a suspension of4′-hydroxy-4-biphenylcarbonitrile (500 mg, 2.56 mmol), alcohol 26b (686mg, 2.56 mmol), and TPP (840 mg, 3.20 mmol) in 25 ml anhydrous ether wasadded DEAD (557 mg, 3.20 mmol) via syringe with stirring and underargon. The reaction mixture was stirred overnight under argon 25° C. Thecrude product was purified via flash chromatography over silica gel withelutions of 98/2, 95/5, and 90/10 (v/v) (Hex/EtOAc), respectively.Evaporation of solvent yielded 765 mg (67%) of a white solid.

4′-(cis-9, cis-12-Octadecadienyloxy)-4-cyanobiphenyl (w372). To asuspension of 4′-hydroxy-4-biphenylcarbonitrile (500 mg, 2.56 mmol),alcohol 26c (681 mg, 2.56 mmol), and TPP (1.008 g, 3.84 mmol) in 25 mlanhydrous ether was added DEAD (669 mg, 3.84 mmol) via syringe withstirring and under argon. The reaction mixture was stirred overnightunder argon at 25° C. The crude product was purified via flashchromatography over silica gel with elutions of 98/2 and 95/5 (v/v)(Hex/EtOAc), respectively. Evaporation of solvent yielded 594 mg (52%)of a white liquid crystal.

Phenylpyrimidines

4′-(Octadecyloxy)-5-nonyl-2-phenylpyrimidine (W398). DEAD (115 mg, 0.66mmol) was added via syringe with stirring and under argon to asuspension of 4′-hydroxy-5-nonyl-2-phenylpyrimidine (152 mg, 0.5.1mmol), 1-octadecanol 26a (152 mg, 0.56 mmol), and TPP (174 mg, 0.66mmol) in 5 ml of anhydrous ether. The reaction mixture was stirredovernight at 25° C., and was then treated with 30% hydrogen peroxide.Ether was added (approx. 20 ml) to the reaction mixture. The organiclayer was separated, washed with brine, and dried over MgSO₄. The crudeproduct was concentrated and purified via flash chromatography oversilica gel with elutions of 95/5, and 90/10 (v/v) (Hex/EtOAc),respectively. Evaporation of solvent yielded 205 mg (73%) of a whitesolid.

4′-(cis-Octadecenyloxy)-5-nonyl-2-phenylpyrimidine (W391). DEAD (109 mg,0.63 mmol), 4′-hydroxy-5-nonyl-2-phenylpyrimidine (150 mg, 0.50 mmol),alcohol 26b (142 mg, 0.53 mmol), and TPP (165 mg, 0.63 mmol) in 5 ml ofanhydrous ether were reacted according to the procedure for compoundW398. The crude product was purified via flash chromatography oversilica gel with elutions of 95/5, and 90/10 (v/v) (Hex/EtOAc),respectively. Evaporation of solvent yielded 154 mg (54%) of a grayliquid crystal.

4′-(cis-9, cis-12-Octadecadienyloxy)-5-nonyl-2-phenylpyrmidine (W390).DEAD (151 mg, 0.87 mmol), 4′-hydroxy-5-nonyl-2-phenylpyrimidine (200 mg,0.67 mmol), alcohol 26c (196 mg, 0.74 mmol), and TPP (229 mg, 0.87 mmol)in 7 ml of anhydrous ether were reacted according to the procedure forcompound W398. The crude product was purified via flash chromatographyover silica gel with elutions of 98/2, 95/5, and 90/10 (v/v)(Hex/EtOAc), respectively. Evaporation of the solvent yielded 234 mg(64%) of a white liquid crystal.

4′-(trans-9, trans-12-Octadecadienyloxy)-5-nonyl-2-phenylpyrimidine(W397). DEAD (113 mg, 0.65 mmol), 4′-hydroxy-5-nonyl-2-phenylpyrimidine(155 mg, 0.52 mmol), alcohol 26d (145 mg, 0.55 mmol), and TPP (170 mg,0.65 mmol) in 4 ml of anhydrous ether were reacted according to theprocedure for compound W398. The crude product was purified via flashchromatography over silica gel with elutions of 95/5 and 90/10 (v/v)(Hex/EtOAc), respectively. Evaporation of solvent yielded 195 mg (69%)of a white solid.

4′-(cis-9-Octadecenoate)-5-nonyl-2-phenylpyrimidine (W393) [Neises, B.and Steglich, W., Agnew Chem. (1978) 90:556].1,3-Dicyclohexylcarbodiimide (DCC) (135 mg, 0.65 mmol) dissolved in 1 mldry dichloromethane was added via syringe with stirring and under argonto a solution of 4′-hydroxy-5-nonyl-2-phenylpyrimidine (150 mg, 0.50mmol), oleic acid (142 mg, 0.50 mmol), and 4-dimethylaminopyridine(DMAP) (18 mg, 0.15 mmol) in 4 ml dry dichloromethane. The reactionmixture was stirred overnight at 25° C. and was then treated with 5%HCl. After extraction with dichloromethane, the organic layer was washedsequentially with saturated sodium bicarbonate and brine, and dried overMgSO₄. The crude product was concentrated and purified via flashchromatography over silica gel with elutions of 98/2, 95/5 and 90/10(v/v) (Hex/EtOAC), respectively. Evaporation of the solvent yielded 226mg (80%) of a white solid.

4′-(cis-9, cis-12-Octadecadienoate)-5-nonyl-phenylpyrimidine (W392). DCC(130 mg, 0.63 mmol) dissolved in 1 ml dry dichloromethane was added viasyringe with stirring and under argon to a solution of4′-hydroxy-5-nonyl-2-phenylpyrimidine (150 mg, 0.50 mmol), linoleic acid(141 mg, 0.50 mmol), and DMAP (18 mg, 0.15 mmol) in 5 ml drydichloromethane. The reaction mixture was stirred overnight at 25° C.and was then treated with 5% HCl. After extraction with dichloromethane,the organic layer was sequentially washed with saturated sodiumbicarbonate and brine, and dried over MgSO₄. The crude product wasconcentrated and purified via flash chromatography over silica gel withelutions of 98/2, 95/5, and 90/10 (v/v) (Hex/EtOAc), respectively.Evaporation of the solvent yielded 227 mg (81%) of a gray liquidcrystal.

Biphenylcarboxylates

(S)-[4″-(1-Methylheptyloxy)-3″-nitrophenyl]-4′-octadecyloxy-4-biphenylcarboxylate(W374). The acid chloride derived from 29a (500 mg, 1.0 mmol) wasdissolved in 15 ml of dry THF and added via syringe with stirring andunder argon, to a solution of 33 (see below) (275 mg, 1.0 mmol) andtriethylamine (115 mg, 1.1 mmol), in 10 ml dry THF. The mixture wasstirred overnight at 25° C. under argon, followed by treatment with 5%HCl and extraction with chloroform. The organic layer was washedsequentially with saturated NaHCO₃ and brine and dried over MgSO₄. Thecrude product was concentrated and purified via flash chromatographyover silica gel 90/10 (v/v) (Hex/EtOAc) to yield 544 mg (74%) of a lightyellow waxy solid. The product was recrystallized from hexanes.

(S)-[4″-(1-Methylheptyloxy)-3″-nitrophenyl]-4′-(cis-9-octadecenyloxy)-4-biphenylcarboxylate(W368). The acid chloride derived from 29b (172 mg, 0.36 mmol) wasdissolved in 2 ml of dry THF and added via syringe with stirring andunder argon, to a solution of 33 (95 mg, 0.36 mmol) and triethylamine(73 mg, 0.72 mmol), in 4 ml dry THF. The mixture was stirred overnightat 25° C. under argon, followed by treatment with 5% HCl and extractionwith chloroform. The organic layer was sequentially washed withsaturated NaHCO₃ and brine and dried over MgSO₄. The crude product wasconcentrated and purified (via flash chromatography over silica gel90/10 (v/v) (Hex/EtOAc). Evaporation of solvent yielded 200 mg (79%) ofa light yellow solid.

(S)-[4″-(1-Methylheptyloxy)-3″-nitrophenyl]4′-(cis-9,cis-12-octadecadienyloxy)-4-biphenylcarboxylate (W358). With stirringand under argon, DCC (312 mg, 1.51 mmol) dissolved in 1 ml drydichloromethane was added via syringe to a suspension of carboxylic acid29c (232 mg, 0.50 mmol), 33 (141 mg, 0.529 mmol), and DMAP (12 mg, 0.10mmol) in 8 ml dry dichloromethane. The solution turned milky yellowduring the addition, and the reaction mixture was stirred under argonfor two days at 25° C. Dichloromethane (20 ml) was then added and thereaction mixture was treated with 5% HCl. The organic layer was washedsequentially with 5% HCl, saturated NaHCO₃, and brine, and dried overMgSO₄. The crude product was purified by flash chromatography oversilica gel with gradual elutions from 98/2 to 80/20 (v/v) (Hex/EtOAc).Evaporation of solvent yielded 170 mg (47%) of a light yellow liquidcrystalline material.

(S)-[4″-(1-Methylheptyloxy)-3″-nitrophenyl]-4′-(cis-9, cis-12,cis-15-octadecatrienyloxy)-4-biphenylcarboxylate (W359). With stirringand under argon, DCC (374 mg, 1.80 mmol) dissolved in 5 ml drydichloromethane was added via syringe to a suspension of carboxylic acid29e ((278 mg, 0.60 mmol), 33 (170 mg, 0.63 mmol), and DMAP (15 mg, 0.012mmol) in 10 ml dry dichloromethane. The solution turned milky yellowduring the addition and the reaction mixture was stirred for 12 hours at25° C., under argon. Dichloromethane (approx. 30 ml) was added and thereaction mixture was treated with 5% HCl. The organic layer wassequentially washed with saturated NaHCO₃ and brine, and was dried overMgSO₄. The crude product was purified by flash chromatography oversilica gel with gradual elutions from 98/2 to 90/10 (v/v) (Hex/EtOAc).Evaporation of the solvent yielded 330 mg (77%) of a light yellowcrystalline material.

(S)-[4″-(1-Methylheptyloxy)-3″-nitrophenyl]-4′-(cis-6, cis-9,cis-12-octadecatrienyloxy)-4-biphenylcarboxylate (W373). The acidchloride derived from 29f (228 mg, 0.48 mmol) was dissolved in 3 ml ofdry THF, and added via syringe with stirring and under argon, to asolution of 33 (127 mg, 0.48 mmol) and triethylamine (58 mg, 0.57 mmol),in 7 ml dry THF. The reaction mixture was stirred overnight at 25° C.,was then treated with 5% HCl and extracted with ether. The organic layerwas washed with saturated NaHCO₃, followed by brine, and dried overMgSO₄. The crude product was concentrated and purified via flashchromatography over silica gel with gradual elutions from 95/5 to 90/10(v/v) (Hex/EtOAc). Evaporation of solvent yielded 163 mg (48%) of alight yellow liquid crystalline material.

(S)-[4″-(1-Methylheptyloxy)-3″-nitrophenyl]-4′-(trans-9,trans-12-octadecadienyloxy)-4-biphenylcarboxylate (W375). DCC (138 mg,0.67 mmol) dissolved in 2 ml dry dichloromethane was added via syringewith stirring and under argon, to a solution of 33 (89 mg, 0.33 mmol),carboxylic acid 29d (155 mg, 0.33 mmol), DMAP (12 mg, 0.1 mmol), andcamphorsulfonic acid (4 mg, 0.017 mmol) in 5 ml dry dichloromethane. Thereaction mixture was stirred for 48 hours at 25° C. under argon and wasthen treated with 5% HCl. The reaction mixture was extracted withdichloromethane and the organic layer was washed with saturated-sodiumbicarbonate followed by brine, and dried over MgSO₄. The crude productwas purified via flash chromatography over silica gel with elutions of98/2, 95/5, and 90/10 (v/v) (Hex/EtOAc), respectively. Evaporation ofthe solvent yielded 111 mg (47%) of a light yellow solid.

Biphenylcarboxylic Acid Intermediates

Methyl-4′-hydroxy-4-biphenylcarboxylate (27). Concentrated sulfuric acid(approximately 4 ml) was carefully added to a solution of4′-hydroxy-4-biphenylcarboxylic acid (Aldrich) (8.20 g, 38.3 mmol) in 1liter of methanol. The reaction mixture was refluxed for three days andthe solvent was evaporated. The resulting solid was filtered, washedwith water, and recrystallized as follows. The crude solid was dissolvedin a minimum amount of hot THF, and approximately three equivalents ofmethanol was added to the solution. The solution was brought to a boil,and water was added with vigorous stirring until the solution remainedcloudy. After cooling, the tan precipitate was filtered, washed withcold ethanol, and air dried to yield 7.57 g (86%) of a tan solid.

Methyl-4′-octadecyloxy-4-biphenylcarboxylate (28a). Potassium carbonate(1.695 g, 12.3 mmol) and cesium carbonate (799 mg, 2.4 mmol) were addedto a solution of the tosylate of 26a (2.60 g, 6.1 mmol), and ester 27(1.468 g, 6.4 mmol) in 60 ml of dry DMF. The solution was stirred for 48hours at 25° C. and was then poured over 200 ml crushed ice.Acidification with 5% HCl resulted in a tan precipitate which wasfiltered, washed with water, and air dried. The product wasrecrystallized from 80/20 (v/v) (Hex/THF) to yield 2.272 g (77%) of atan powder.

Methyl-4′-(cis-9-octadecenyloxy)-4-biphenylcarboxylate (28b). DEAD (676mg, 3.88 mmol) was added via syringe with stirring and under argon, to asolution of ester 27 (590 mg, 2.59 mmol), alcohol 26b (707 mg, 2.64mmol), and TPP (1.018 g, 3.88 mmol) in 8 ml dry THF. The reactionmixture was stirred overnight under argon at 25° C. and then treatedwith 30% hydrogen peroxide. Ether was added (approximately 20 ml) andthe organic layer was separated, washed with brine, and dried overMgSO₄. The crude product was adsorbed onto silica gel and purified viaflash chromatography with elutions of 95/5 and 90/10 (v/v) (Hex/EtOAc),respectively. Evaporation of solvent yielded 505 mg (41%) of a whitesolid.

Methyl-4′-(cis-9,cis-12-octadecadienyloxy)-4-biphenylcarboxylate (28c).DEAD (818 mg, 4.70 mmol) was slowly added via syringe, with stirring andunder argon, to a solution of ester 27 (857 mg, 3.76 mmol), alcohol 26c(1.0 g, 3.76 mmol), and triphenylphosphine (1.232 g, 4.70 mmol) in 31 mldry THF. The reaction mixture was stirred overnight and was then treatedwith 30% H₂O₂. Ether was added (approximately 30 ml) and the organiclayer was separated, washed with brine, and dried over MgSO₄. Thesolvent was evaporated and the crude product was adsorbed onto silicagel and purified via flash chromatography with gradual elutions from98/2 to 90/10 (v/v) (Hex/EtOAc). Evaporation of solvent yielded 1.411 g(79%) of a white solid.

Methyl-4′-(trans-9,trans-12-octadecadienyloxy)-4-biphenylcarboxylate(28d). DEAD (392 mg, 2.25 mmol) was slowly added via syringe, withstirring and under argon, to a solution of ester 27 (343 mg, 1.5 mmol),alcohol 26d (400 mg, 1.5 mmol), and TPP (592 mg, 2.25 mmol) in 11 mlanhydrous ether. The reaction mixture was stirred overnight under argonat 25° C. and then was treated with 30% H₂O₂. Ether was added(approximately 20 ml) and the organic layer was separated, washed withbrine, and dried over MgSO₄. The crude product was concentrated andpurified-via flash chromatography over silica gel, with elutions of98/2, 95/5 and 90/10 (v/v) (Hex/EtOAc), respectively. Evaporation ofsolvent yielded 214 mg (30%) of a white solid.

Methyl-4′-(cis-9,cis-12,cis-15-octadecatrienyloxy)-4-biphenylcarboxylate(28e). DEAD (463 mg, 2.66 mmol) was slowly added via syringe, withstirring and under argon, to a solution of ester 27 (406 mg, 1.78 mmol),alcohol 26e (469 mg, 1.78 mmol), and TPP (699 mg, 2.66 mmol) in 30 mldry THF. The reaction mixture was refluxed for 24 hours, cooled andtreated with 30% H₂O₂. Ether was added (approximately 20 ml) and theorganic layer was separated, washed with brine, and dried over MgSO₄.The solvent was evaporated and the crude product was purified via flashchromatography over silica gel 90/10 (v/v, Hex/EtOAc). Evaporation ofsolvent yielded 324 mg (38%) of a white solid.

Methyl-4′-(cis-6,cis-9,cis-12-octadecatrienyloxy)-4-biphenylcarboxylate(28f). DEAD (763 mg, 4.38 mmol) was added via syringe, with stirring andunder argon, to a solution of ester 27 (800 mg, 3.5 mmol), alcohol 26f(926 mg, 3.5 mmol), and TPP (1.150 g, 4.38 mmol) in 25 ml dry, THF. Thereaction mixture was stirred overnight under argon at 25° C. and thenwas treated with 30% H₂O₂. Ether was added (approximately 20 ml) and theorganic layer was separated, washed with brine, and dried over MgSO₄.The crude product was adsorbed onto silica gel and purified via flashchromatography with gradual elutions from 95/5 to 80/20 (v/v)(Hex/EtOAc). Evaporation of solvent yielded 1.034 g (62%) of a lightyellow waxy solid.

4′-Octadecyloxy-4-biphenylcarboxylic acid (29a). Lithium hydroxidemonohydrate (874 mg, 20.8 mmol) was added to a suspension of the ester28a (2.00 g, 4.17 mmol), 50 ml water, and 200 ml THF. The mixture wasrefluxed for 48 hours and then was acidified with concentrated HCl.Water (150 ml) was added and the solution was cooled. The resulting tanprecipitate was filtered and washed with water. The tan precipitate wasdissolved in 100 ml hot THF and hexanes were added until the solutionremained cloudy with stirring. After cooling, crystals were filtered toyield 1.4 g of a light yellow solid, and a second crop of crystals wasisolated for a total yield of 1.67 g (86%). The product was used withoutfurther purification.

4′-(cis-9-octadecenyloxy)-4-Biphenylcarboxylic acid (29b). Water(approximately 15 ml) was added to a solution of ester 28b (486 mg, 1.00mmol) in 50 ml of an 80/20 (v/v) (methanol/THF) solution, until itremained milky white with vigorous stirring. To this suspension wasadded lithium hydroxide monohydrate (213 mg, 5.1 mmol), the reactionmixture was refluxed overnight and then was acidified with concentratedHCl. Water (approximately 20 ml) was added and the solution was cooled,filtered, washed several times with water, and air dried, yielding 422mg (89%) of a white waxy powder.

4′-(cis-9,cis-12-octadecadienyloxy)-4-biphenylcarboxylic acid (29c). Toester 28c (989 mg, 2.07 mmol) was added 100 ml of an 80/20 (v/v)(methanol/THF) solution. With vigorous stirring, water (approximately 20ml) was added until the solution remained milky white. To thissuspension was added lithium hydroxide monohydrate (436 mg, 10.4 mmol),the reaction mixture was refluxed for 6 hours and then acidified withconcentrated HCl. Water (approximately 50 ml) was added, the reactionmixture was cooled, filtered, and washed several times with water toyield 933 mg (97%) of a white waxy powder. The crude product was usedwithout further purification.

4′-(trans-9,trans-12-octadecadienyloxy)-4-biphenylcarboxylic acid (29d).To ester 28d (211 mg, 0.44 mmol) was added 40 ml of an 80/20 (v/v)(methanol/THF) solution. Water (approximately 5 ml) was added withvigorous stirring until the solution remained milky white. To thissuspension was added lithium hydroxide monohydrate (93 mg, 2.2 mmol),the reaction mixture was refluxed overnight and was then acidified withconcentrated HCl. Water (approximately 20 ml) was added and the reactionmixture was cooled, filtered and the product was washed several timeswith water. The product was air dried yielding 172 mg (84%) of a whitepowder.

4′-(cis-9,cis-12,cis-15-octadecatrienyloxy)-4-biphenylcarboxylic acid(29e). To ester 28e (320 mg, 0.67 mmol) was added 50 ml of an 80/20(v/v) (methanol/THF) solution. With vigorous stirring, water(approximately 10 ml) was added until the solution remained milky white.To this suspension was added lithium hydroxide monohydrate (142 mg, 3.34mmol), the reaction mixture was refluxed for six hours and was thenacidified with concentrated HCl. Water (approximately 20 ml) was added,the reaction mixture was cooled, filtered, washed several times withwater, and air dried to yield 282 mg (91%) of a white waxy powder.

4′-(cis-6,cis-9,cis-12-octadecatrienyloxy)-4-biphenylcarboxylic acid(29f). To ester 28f (230 mg, 0.48 mmol) was added 30 ml of an 80/20(v/v) (methanol/THF) solution. With vigorous stirring, water was addeduntil the solution remained milky white (approximately 5 ml). To thissuspension was added lithium hydroxide monohydrate (102 mg, 2.4 mmol),the reaction mixture was refluxed overnight and was then acidified withconcentrated HCl. Water (approximately 15 ml) was added, the reactionmixture was cooled, filtered, washed several times with water, and airdried to yield 220 mg (99%) of a light yellow waxy powder.

Hydroquinone Fragment

4-(1Hydroxy)-phenylbenzoate (30). This material was obtained fromLancaster Chemicals.

4(Hydroxy)-3-(nitro)-phenylbenzoate (31) [Keller, P., Bull. Soc. Chim.Fr. (1994) 131:27]. To a solution of 4-(hydroxy)-phenylbenzoate 30 (8.0g, 37.38 mmol), NaNO₃ (3.336 g, 39.25 mmol), 45 ml H₂O, 75 mldichloromethane, and 150 ml ether, was carefully added 9 mmlconcentrated HCl. With vigorous stirring acetic anhydride (1 ml) wasadded. The reaction mixture was stirred overnight and then the organiclayer was separated, washed with brine, and dried over magnesiumsulfate. Evaporation of solvent yielded an orange powder which wasrecrystallized twice from ethanol to yield 7.304 g of yellow crystals.The mother liquor was concentrated and purified via flash chromatographyover silica gel (30/60/10, v/v/v, dichloromethane/Hex/EtOAc) to yield anadditional 1.103 g product. Total yield was 8.407 g (87%) of a yellowsolid.

(S)-4-(1-Methylheptyloxy)-3-nitro-phenylbenzoate (32a). DEAD (2.42 g,13.9 mmol) was added via syringe with stirring and under argon to asolution of 31 (2.41 g, 9.3 mmol), TPP (3.66 g, 13.9 mmol), and(R)-2-octanol in 120 ml of anhydrous ether. The reaction mixture wasstirred overnight at 25° C. and then was treated with 30% hydrogenperoxide. The organic layer was separated, washed with brine, and driedover magnesium sulfate. The crude product was purified via flashchromatography over silica gel (90/10, v/v, Hex/EtOAc) to yield 2.99 g(87%) of a yellow oil.

4-(Heptyloxy)-3-nitro-phenylbenzoate (32b). DEAD (222 mg, 1.27 mmol),phenol 31 (250 mg, 1.02 mmol), 1-heptanol (130 mg, 1.12 mmol), and TPP(334 mg, 1.27 mmol) in 10 ml anhydrous ether were reacted according tothe procedure for compound 32a. The crude material was purified viaflash chromatography over silica gel with gradual elutions from95/5-90/10 (v/v) (Hex/EtOAc). Evaporation of solvent yielded 294 mg(84%) of a light green oil.

(S)-4-(1-methylheptyloxy)-3-nitrophenol (33). Compound 32a (380 mg, 1.02mmol) was dissolved in 10 ml methanol, and water (approximately 3 ml)was added until the solution remained milky yellow with vigorousstirring. Lithium hydroxide monohydrate (258 mg, 6.1 mmol) was added,the reaction mixture was stirred for six hours at 25° C., and then wasacidified with concentrated HCl. The reaction mixture was extracted withdichloromethane (30 ml). The organic layer was separated, washed withsaturated sodium bicarbonate, followed by brine, and dried overmagnesium sulfate. The solvent was evaporated and the crude product waspurified via flash chromatography over silica gel (50/50, v/v,Hex/EtOAc) to yield 269 mg (98%) of an orange oil.

Biphenylbenzoates

(S)-[4′-(1-Methylheptyloxy)-3′-(nitro)-biphenyl]-4-octadecyloxy-benzoate(W412). DCC (143 mg, 0.69 mmol) dissolved in 1 ml dichloromethane wasadded via syringe, with stirring and under argon, to a solution of theacid 36a (254 mg, 0.63 mmol), the phenol 39a (226 mg, 0.66 mmol), andDMAP (31 mg, 0.25 mmol) in 10 ml dichloromethane. The reaction mixturewas stirred overnight at 25° C. and then was treated with 5% HCl.Dichloromethane (approximately 15 ml) was added, and the organic layerwas separated, washed with saturated NaHCO₃, followed by brine, anddried over MgSO₄. The crude product was purified via flashchromatography over silica gel with gradual elutions from 98/2 to 80/20(v/v) (Hex/EtOAc). Evaporation of the solvent yielded 275 mg (59%) of ayellow solid. The product was then recrystallized from hexanes.

(S)-[4′-(1-Methylheptyloxy)-3′-(nitro)-biphenyl]-4-(cis-9-octadecenyloxy)benzoate(W452). The phenol 39a (130 mg, 0.379 mmol), carboxylic acid 36b (162mg, 0.42 mmol), DCC (94 mg, 0.45 mmol), and DMAP (18 mg, 0.15 mmol) in 4ml dichloromethane were reacted according to the procedure for compoundW412. The crude product was purified via flash chromatography oversilica gel with gradual elutions from 98/2-90/10 (v/v, Hex/EtOAc).Evaporation of the solvent yielded 195 mg (72%) of a light green liquidcrystalline material. This was precipitated from hexanes.

(S)-[4′-(1-Methylheptyloxy)-3′-(nitro)-biphenyl]-4-(cis-9,cis-12-octadecanoyloxy)benzoate (W360). DCC (235 mg, 1.14 mmol),carboxylic acid 36c (220 mg, 0.568 mmol), phenol 39a (195 mg, 0.568mmol), and DMAP (28 mg, 0.228 mmol) in 6 ml dichloromethane were reactedaccording to the procedure for compound W412. The crude product waspurified via flash chromatography over silica gel with gradual elutionsfrom 98/2 to 80/20 (v/v, Hex/EtOAc). Evaporation of the solvent yielded290 mg (72%) of a yellow-green liquid crystalline material. This wasprecipitated from hexanes.

(S)-[4′-(1-Methylheptyloxy)-3′-(nitro)-biphenyl]-4-(trans-9,trans-12-octadecanoyloxy)-benzoate (W410). DCC (195 mg, 0.95 mmol),carboxylic acid 36d (333 mg, 0.86 mmol), phenol 39a (310 mg, 0.90 mmol),and DMAP (42 mg, 0.34 mmol) in 8 ml dichloromethane were reactedaccording to the procedure for compound W412. The crude product waspurified via flash chromatography over silica gel with gradual elutionsfrom 98/2 to 80/20 (v/v, Hex/EtOAc). Evaporation of the solvent yielded460 mg (75%) of a yellow-green liquid crystalline material. This wasprecipitated from hexanes.

(S)-[4′-(1-Methylheptyloxy)-3′-(nitro)-biphenyl]-4-decyloxybenzoate(W317). The synthesis and physical data of this material have beenreported elsewhere. (See WO 92/03427.)

(S)-[4′-(1-Methylheptyloxy)-3′-(nitro)-biphenyl]-4-(trans-2-decenyloxy)-benzoate(W422). The phenol 39a (310 mg, 0.90 mmol), carboxylic acid 36g (250 mg,0.90 mmol), DCC (205 mg, 0.99 mmol), and DMAP (44 mg, 0.36 mmol) in 9 mldichloromethane were reacted according to the procedure for compoundW412. The crude product was purified via flash chromatography oversilica gel with gradual elutions from 95/5-90/10 (v/v) (Hex/EtOAc).Evaporation of the solvent yielded 393 mg (72%) of a light green liquidcrystalline material. This was precipitated from hexanes.

(S)-[4′-(1-Methylheptyloxy)-3′-(nitro)-biphenyl]-4-(trans-3-decenyloxy)-benzoate(W425). The phenol 39a (394 mg, 1.15 mmol), carboxylic acid 36h (317 mg,1.15 mmol), DCC (260 mg, 1.25 mmol), and DMAP (56 mg, 0.46 mmol) in 12ml dichloromethane were reacted according to the procedure for compoundW412. The crude product was purified via flash chromatography oversilica gel with gradual elutions from 95/5-90/10 (v/v, Hex/EtOAc).Evaporation of the solvent yielded 536 mg (78%) of a light green liquidcrystalline material. This was precipitated from hexanes.

(S)-[4′-(1-Methylheptyloxy)-3′-(nitro)-biphenyl]-4-(trans-4-decenyloxy)-benzoate(W411). DCC (274 mg, 1.33 mmol), carboxylic acid 36i (334 mg, 1.21mmol), phenol 39a (436 mg, 1.27 mmol), and DMAP (59 mg, 0.48 mmol) in 12ml dichloromethane were reacted according to the procedure for compoundW412. The crude product was purified via flash chromatography oversilica gel with gradual elutions from 98/2 to 80/20 (v/v, Hex/EtOAc).Evaporation of the solvent yielded 549 mg (76%) of a yellow-green liquidcrystalline material. This was precipitated from hexanes.

Benzoic Acid Fragment

Methyl-4-octadecyloxy-benzoate (35a). DEAD (400 mg, 2.3 mmol) was slowlyadded via syringe, with stirring and under argon, to a solution of thephenol 34 (281 mg, 1.85 mmol), alcohol 26a (500 mg, 1.85 mmol), and TPP(606 mg, 2.3 mmol) in 18 ml anhydrous ether. The reaction mixture wasstirred overnight at 25° C. and then treated with 30% hydrogen peroxide.Ether was added (10 ml), the organic layer was separated, washed withbrine, and dried over MgSO₄. The crude product was concentrated andpurified via flash chromatography over silica gel (95/5, v/v, Hex/EtOAcand 5% dichloromethane). Evaporation of the solvent yielded 544 mg (73%)of a colorless liquid.

Methyl-4-(cis-9,cis-12-octadecanoyloxy)-benzoate (35c). DEAD (515 mg,2.96 mmol), phenol 34 (300 mg, 1.97 mmol), alcohol 26c (551 mg, 2.07mmol), and TPP (776 mg, 2.96 mmol) in 16 ml anhydrous ether were reactedaccording to the procedure for compound 35a. The crude product waspurified via flash chromatography over silica gel 95/5 (Hex/EtOAc).Evaporation of the solvent yielded 582 mg (74%) of colorless liquid.

Methyl-4-(trans-9,trans-12-octadecanoyloxy)-benzoate (35d). DEAD (515mg, 2.96 mmol), phenol 34 (300 mg, 1.97 mmol), alcohol 26d (551 mg, 2.07mmol), and TPP (776 mg, 2.96 mmol) in 16 ml anhydrous ether were reactedaccording to the procedure described for compound 35a. The crude productwas purified via flash chromatography over silica gel with gradualelutions from 98/2 to 90/10 (v/v, Hex/EtOAc). Evaporation of the solventyielded 575 mg (73%) of colorless liquid.

Methyl-4-(trans-2-decenyloxy)-benzoate (35g). Phenol 34 (486 mg, 3.2mmol), 2-decenol 26g (500 mg, 3.2 mmol), TPP (965 mg, 3.68 mmol), andDEAD (641 mg, 3.68 mmol) in 32 ml ether were reacted according to theprocedure for compound 35a. The crude product was purified via flashchromatography over silica gel with gradual elutions from 95/5-90/10(v/v, Hex/EtOAc). Evaporation of solvent yielded 603 mg (65%) ofcolorless needles.

Methyl-4-(trans-3-decenyloxy)-benzoate (35h). Ester 34 (500 mg, 3.29mmol), 3-decenol 26h (514 mg, 3.29 mmol), TPP (992 mg, 3.78 mmol), DEAD(658 mg, 3.78 mmol), and 33 ml ether were reacted according to theprocedure for compound 35a. The crude product was purified via flashchromatography over silica gel with gradual elutions from 95/5-90/10(v/v, Hex/EtOAc). Evaporation of solvent yielded 810 mg (85%) ofcolorless liquid which was not quite pure. The product was used withoutfurther purification.

Methyl-4-(trans-4-decenyloxy)-benzoate (35i). DEAD (641 mg, 3.68 mmol),phenol 34 (487 mg, 3.2 mmol), alcohol 26i (500 mg, 3.2 mmol), and TPP(966 mg, 3.68 mmol) in 16 ml anhydrous ether were reacted according tothe procedure for compound 35a. The crude product was purified via flashchromatography over silica gel with gradual elutions from 95/5 to 90/10(v/v, Hex/EtOAc). Evaporation of the solvent yielded 748 mg (80%) ofcolorless liquid.

Methyl-4-(trans-5-decenyloxy)-benzoate (35j). DEAD (256 mg, 1.47 mmol),phenol 34 (194 mg, 1.28 mmol), alcohol 26j (200 mg, 1.28 mmol), and TPP(386 mg, 1.47 mmol) in 13 ml anhydrous ether were reacted according tothe procedure for compound 35a. The crude product was purified via flashchromatography over silica gel with gradual elutions from 95/5 to 90/10(v/v, Hex/EtOAc). Evaporation of the solvent yielded 266 mg (72%) ofcolorless liquid.

4-octadecyloxy-benzoic acid (36a). The ester 35a (405 mg, 1.0 mmol) wasdissolved in 15 ml THF and 50 ml methanol was added. Water(approximately 10 ml) was added until the solution remained cloudy withvigorous stirring, at which time lithium hydroxide monohydrate (840 mg,20.0 mmol) was added. The reaction mixture was refluxed overnight,acidified with concentrated HCl and cooled. The precipitate wasfiltered, washed with water and air dried to yield 279 mg (71%) of awhite powder.

4-(cis-9, cis-12-octadecanoyloxy)-benzoic acid (36c). The starting ester35c (520 mg, 1.3 mmol) was dissolved in 40 ml THF. Water (approximately10 ml) was added until the solution remained cloudy, at which timelithium hydroxide monohydrate (273 mg, 6.5 mmol) was added. The reactionmixture was refluxed overnight, acidified with concentrated HCl andextracted with ether. The organic layer was washed with brine and driedover MgSO₄. Evaporation of the solvent yielded 481 mg (96%) of a viscouswhite liquid crystalline material. Further purification was possible viaflash chromatography (50/50, v/v, Hex/EtOAc) over silica gel, howeverthe crude product was sufficiently pure to be used in the next step.

4-(trans-9, trans-12-octadecanoyloxy)-benzoic acid (36d). The ester 35d(491 mg, 1.23 mmol) was dissolved in 40 ml THF. Water (approximately 10ml) was added until the solution remained cloudy, at which time lithiumhydroxide monohydrate (257 mg, 6.1 mmol) was added. The reaction mixturewas refluxed overnight, acidified with concentrated HCl and extractedwith ether. The organic layer was washed with brine and dried overMgSO₄. The crude product was purified via flash chromatography oversilica gel (50/50, v/v, Hex/EtOAc) to yield 380 mg (80%) of a whitesolid.

4-(trans-2-Decenyloxy)-benzoic acid (36g). The ester 35g 565 mg, 1.95mmol), and lithium hydroxide monohydrate (817 mg, 19.5 mmol) in 20 mlmethanol were reacted according to the procedure for compound 36a. Theyield was 482 mg (89% of a white powder.

4-(trans-3-Decenyloxy)-benzoic acid (36h). Ester 35h (600 mg, 2.07mmol), and lithium hydroxide monohydrate (867 mg, 20.7 mmol) in 20 mlmethanol were reacted according to the procedure for compound 36a. Theyield was 500 mg (87%) of a white powder which was not quite pure (95%).The product was used without further purification.

4-(trans-4-decenyloxy)-benzoic acid (36i). The ester 35i (500 mg, 1.7mmol) was dissolved in 50 ml methanol. Water (approximately 10 ml) wasadded until the solution remained cloudy, at which time lithiumhydroxide monohydrate (723 mg, 17.0 mmol) was added. The reactionmixture was refluxed overnight and acidified with concentrated HCl.Water was added (approximately 30 ml), the mixture was cooled, filtered,washed with water and allowed to air dry yielding 400 mg (84%) of awhite powder.

4-(trans-5-decenyloxy)-benzoic acid (36j). The ester 35j (240 mg, 0.83mmol) was dissolved in 15 ml methanol. Water (approximately 2 ml) wasadded until the solution remained cloudy with vigorous stirring, atwhich time lithium hydroxide monohydrate (347 mg, 8.3 mmol) was added.The reaction mixture was refluxed overnight and acidified withconcentrated HCl. Water was added (approximately 10 ml), the mixture wascooled, filtered, washed with water and allowed to air dry yielding 183mg (80%) of a white powder.

Biphenol Fragment

4′-(hydroxy)-3′-(nitro)-4-biphenylbenzoate (37). Concentrated nitricacid (0.36 ml) was added over a 30 minute period to a cooled suspension(5-10° C.) of 4′-(benzoyl)-4-biphenol [Naciri, J. et al., Chem. Mater.(1995) 7:1397] (500 mg, 1.7 mmol) in 12 ml glacial acetic acid. Thereaction mixture was stirred for 1 hour as it slowly warmed to roomtemperature, then water was added and the reaction mixture was cooled.The resulting precipitate was filtered, washed with water and air dried.The product was recrystallized from a solution of ethanol/THF (3/1, v/v)to yield 455 mg of product. The mother liquor was then adsorbed ontosilica gel and purified via flash chromatography [50/45/5, v/v/v,Hex/dichloromethane/EtOAc]. Evaporation of solvent yielded an additional100 mg, for a total yield of 555 mg (97%) of a yellow solid.

4′-(1-Methylheptyloxy)-3′-(nitro)-4-biphenylbenzoate (38a). Phenol 37(700 mg, 2.1 mmol), R-2-octanol (340 mg, 2.6 mmol), TPP (821 mg, 3.1mmol), and DEAD (545 mg, 3.1 mmol) in 21 ml dry THF were reactedaccording to the procedure for compound 35a. The crude product waspurified via flash chromatography over silica gel [50/45/5, v/v/v,Hex/dichloromethane/EtOAc]. Evaporation of solvent yielded 833 mg (89%)of a viscous yellow oil.

(S)-4′-(1-Methylnonyloxy)-3′-(nitro)-4-biphenylbenzoate (38b). Phenol 37(529 mg, 1.58 mmol), R-2-decanol (250 mg, 1.58 mmol), TPP (621 mg, 2.37mmol), and DEAD (412 mg, 2.37 mmol) in 16 ml dry THF were reactedaccording to the procedure for compound 35a. The crude product waspurified via flash chromatography over silica gel with gradual elutionsfrom 95/5-80/20 (v/v, Hex/EtOAc). Evaporation of solvent yielded 504 mg(67%) of a light green viscous oil.

4′-(1-Methylheptyloxy)-3′-(nitro)-4-biphenol (39a). Ester 38a (288 mg,0.64 mmol) was dissolved in 10 ml THF and 5 ml methanol. Water was addedwith vigorous stirring until the solution remained cloudy, followed bythe addition of lithium hydroxide monohydrate (135 mg, 3.2 mmol). Thereaction mixture was stirred overnight and was then acidified withconcentrated HCl. The reaction mixture was separated with ether. Theorganic layer was washed with brine and dried over MgSO₄. The crudeproduct was purified via flash chromatography over silica gel [60/40,v/v, Hex/EtOAc]. Evaporation of solvent yielded 190 mg (86%) of aviscous orange oil.

(S)-4′(1-Methylnonyloxy)-3′-(nitro)-4-biphenol (39b). Ester 38b (470 mg,0.989 mmol), and lithium hydroxide monohydrate (207 mg, 4.90 mmol) in 20ml THF were reacted according to the procedure for compound 39a. Thecrude product was purified via flash chromatography over silica gel withgradual elutions from 80/20-50/50 (v/v, Hex/EtOAc). Evaporation ofsolvent yielded 321 mg (88%) of a viscous orange oil.

Example 1.6

Electroclinic Tilt Measurements

Electroclinic tilt angles were measured using a DC field supplied by alow frequency square wave generator. The cell was rotated to extinctionand the field was then reversed. The cell was rotated back to extinctionto yield 2θ. The LC cells varied from the commercially available 4μHamlin type cell, to standard ITO glass slides coated with a rubbednylon alignment layer and separated with glass spacers of knownthickness.

Example 1.7

Dichroic Ratio Measurements

The visible light dichroic measurements were performed on a HewlettPackard model HP 8452 diode array spectrometer, fitted with atemperature controller (Model: HP 8909A). The cells consisted of twoglass plates coated with a rubbed nylon alignment layer. A rotatingpolarizing stage was fitted between the cell and the light source.

Example 1.8

Bis-Chiral Tailed Biphenylcarboxylates

(S,S)-[4″-(1-Methylheptyloxy)-3″-nitrophenyl]-4′-(1-methylheptyloxy)-3′-(nitro)-4-biphenylcarboxylate(W363). DCC (193 mg, 0.93 mmol), carboxylic acid 42a (315 mg, 0.85mmol), phenol 33 (238 mg, 0.89 mmol), and DMAP (41 mg, 0.34 mmol) in 7ml dichloromethane were reacted according to the procedure for compound16. The crude product was purified via flash chromatography over silicagel with gradual elutions from 95/5 to 65/35 (Hex/EtOAc). Evaporation ofthe solvent yielded 410 mg (78%) of a yellow solid, which was thenprecipitated from hexanes.

(S,S)-[4′″-(1-Methylheptyloxy)-3′″-(nitro)-biphenyl]-4′(1-methylheptyloxy)-3′-(nitro)-4-biphenylcarboxylate(W364). DCC (306 mg, 1.48 mmol), carboxylic acid 42a (500 mg, 1.35mmol), phenol 39a (485 mg, 1.41 mmol), and DMAP (66 mg, 0.54 mmol) in 13ml dichloromethane were reacted according to the procedure for compound16. The crude product was purified via flash chromatography over silicagel with gradual elutions from 98/2 to 65/35 (Hex/EtOAc). Evaporation ofthe solvent yielded 760 mg (81%) of a yellow solid, which was thenprecipitated from hexanes.

(S,S)-[4″-(1-Methylheptyloxy)-3′″-nitrophenyl]-4′-(1-methylnonyloxy)-3′-(nitro)-4-biphenylcarboxylate(W365). DCC (57 mg, 0.27 mmol), carboxylic acid 42b (100 mg, 0.25 mmol),phenol 33 (67 mg, 0.25 mmol), and DMAP (12 mg, 0.10 mmol) in 3 mldichloromethane were reacted according to the procedure for compound 16.The crude product was purified via flash chromatography over silica gelwith gradual elutions from 95/5 to 80/20 (Hex/EtOAc). Evaporation of thesolvent yielded 102 mg (63%) of a yellow solid, which was thenprecipitated from hexanes.

(S,S)-[4′″-(1-Methylnonyloxy)-3′″-(nitro)-biphenyl]-4′-(1-methylnonyloxy)-3′-(nitro)-4-biphenylcarboxylate(W424). Carboxylic acid 42b (100 mg, 0.25 mmol), phenol 39b (93 mg, 0.25mmol), DCC (65 mg, 0.31 mmol), and DMAP (15 mg, 0.12 mmol) in 4 mldichloromethane was reacted according to the procedure for compound 16.The crude product was purified via flash chromatography over silica gelwith gradual elutions from 9515-50/50 (Hex/EtOAc). Evaporation ofsolvent yielded 137 mg (73%) of a yellow solid, which was thenprecipitated from hexanes.

o-Nitro-Biphenylcarboxylic Acid Fragment

Methyl-4′-(hydroxy)-3′-(nitro)-4-biphenylcarboxylate (40). Concentratednitric acid (1.8 ml) was carefully added to a cooled suspension (5-10°C.) of phenol 27 (2.0 mg, 8.8 mmol) in 60 ml of glacial acetic acid. Thereaction mixture was stirred for one hour and was then allowed to warmto room temperature and stirred for an additional 30 minutes. Water wasadded (50 ml) and the reaction mixture was cooled, filtered, and washedwith water to yield a yellow powder. The crude product was purified viaflash chromatography through a small pad of silica gel with elutions of80/20 and 50/50 (Hex/EtOAc), respectively. Evaporation of the solventyielded 2.23 g (93%) of a bright yellow solid.

(S)-Methyl-4′-(1-methylheptyloxy)-3′-(nitro)-4-biphenylcarboxylate(41a). DEAD (1.097 g, 6.3 mmol), phenol 40 (1.50 g, 5.5 mmol),R-2-octanol (751 mg, 5.77 mmol), and TPP (1.657 g, 6.3 mmol) in 55 mlanhydrous ether were reacted according to the procedure for compound35a. The crude product was concentrated and purified via flashchromatography over silica gel with gradual elutions from 90/10 to 65/35(Hex/EtOAc). Evaporation of the solvent yielded 1.90 g (90%) of yellowsolid.

(S)-Methyl-4′-(1-methylnonyloxy)-3′-(nitro)-4-biphenylcarboxylate (41b).DEAD (323 mg, 1.85 mmol), phenol 40 (440 mg, 1.61 mmol), R-2-decanol(268 mg, 1.69 mmol), and TPP (486 mg, 1.85 mmol) in 16 ml anhydrousether were reacted according to the procedure for compound 35a. Thecrude product was concentrated and purified via flash chromatographyover silica gel with gradual elutions from 95/5 to 65/35 (Hex/EtOAc).Evaporation of the solvent yielded 439 mg (66%) of a yellow solid.

(R)-Methyl-3′-(nitro)-4′-(1-methylheptyloxy)-4-biphenylcarboxylate(41c). DEAD (151 mg, 0.87 mmol), TPP (228 mg, 0.87 mmol), phenol 40 (190mg, 0.69 mmol), and S-2-octanol (95 mg, 0.73 mmol) in 7 ml anhydrousether were reacted according to the procedure for compound 35a. Thecrude product was purified via flash chromatography over silica gel withgradual elutions from 90/10 to 50/50 (Hex/EtOAc). Evaporation of solventyielded 183 mg (68%) of a light yellow solid.

(S)-4′-(1-Methylheptyloxy)-3′-(nitro)-4-biphenylcarboxylic acid (42a).Ester 41a (1.679 g, 4.36 mmol) was dissolved in 10 ml of THF, and withvigorous stirring methanol (40 ml) was added, followed by water(approximately 10 ml) until the solution remained milky white. To thissuspension was added lithium hydroxide monohydrate (1.83 g, 43.6 mmol).The reaction mixture was refluxed overnight and was then acidified withconcentrated HCl. Brine was added, the reaction mixture was extractedwith ether and the organic layer was washed with brine and dried overMgSO₄. Evaporation of the solvent yielded 1.486 g (92%) of a lightyellow solid.

(S)-4′-(1-Methylnonyloxy)-3′-(nitro)-4-biphenylcarboxylic acid (42b).Ester 41b (390 mg, 0.94 mmol) was dissolved in 3. ml THF and 15 mlmethanol. Water was added with vigorous stirring until the solutionremained cloudy, followed by the addition of lithium hydroxidemonohydrate (56 mg, 1.30 mmol). After refluxing overnight, the solutionwas acidified with concentrated HCl and extracted with ether. Theorganic layer was washed with brine and dried over MgSO₄. Evaporation ofthe solvent yielded 323 mg (86%) of a yellow solid.

Example 1.9

Azo-Dyes: Side by Side Dimers

Mixed Tolan-Biphenylcarboxylate System

(S)-[4″-(1-Methylheptyloxy)-5″-(N,N-dimethylamino)-2″-[(S)-2′″-(1-methylheptyloxy)-5′″-[4″″-carboxy-(4′″″-dodecyloxyphenyl)-phenylacetylenyl]-4′″-nitro-phenylazo]-phenyl]-4′-(decyloxy)-4-biphenylcarboxylate(W421) [Stephens, R. D. and Castro, C., J. Org. Chem. (1963) 28:3313;Sonogashira, K. et al., Tet. Lett. (1975) 50:4467]. To a solution of theazo-dye 46 (266 mg, 0.265 mmol) and the acetylide 47 (129 mg, 0.318mmol) in pyridine (27 ml), was added copper iodide (20 mg),copper(acetate)₂ monohydrate (20 mg), andtetrakis(triphenylphosphine)palladium(0) catalyst (50 mg). The reactionmixture was stirred for 48 hours at 25° C. Ethyl acetate (approximately15 ml) was added, followed by brine, and the organic layer wasseparated. The organic layer was washed twice with 10% HCl, followed bysaturated sodium bicarbonate and brine. After drying over MgSO₄, thecrude product was adsorbed onto silica gel and purified via flashchromatography with gradual elutions from 90/5/5 to 80/15/5 (v/v/v)(Hex/EtOAc/dichloromethane). Evaporation of the solvent yielded 79 mg(23%) of a red solid. An additional 123 mg of the starting azo-dye wasrecovered for an adjusted yield of 43%.

(S)-4-(1-Methylheptyloxy)-3-(N,N-dimethylamino)-phenol (43a) [Hunig, S.and Baron; W., Ber. (1957) 90:395]. Iodomethane (16 ml, 257 mmol) wasadded to a stirred solution of analine 48a (1.10 g, 3.22 mmol),anhydrous potassium carbonate (1.337 g, 9.67 mmol), and DMF (32 ml). Thereaction mixture was stirred for 2 hours at 25° C. and the excessiodomethane was evaporated off. Ethanolamine (65 ml) was added and thereaction mixture was refluxed (165° C.) for 2 hours. The reactionmixture was cooled, diluted with water, and extracted twice with ethylacetate. The combined organic layers were washed with brine and driedover MgSO₄. The crude product was concentrated and purified via flashchromatography over silica gel, with gradual elutions from 80/20 to50150 (Hex/EtOAc). Evaporation of solvent yielded 695 mg (81%) of ayellow oil.

(S)4-(1-Methylheptyloxy)-3-(N,N-dimethyl)-aminophenol (43b). Methyliodide (7.9 ml), compound 48b (551 mg, 1.68 mmol), ethanolamine (34 ml),and potassium carbonate (698 mg), in 16 ml DMF were reacted according tothe procedure for compound 43a. The crude product was purified via flashchromatography over silica gel with gradual elutions from 80/20-50/50(Hex/EtOAc). Evaporation of solvent yielded 260 mg (61%) of a viscousyellow oil.

(S)-5-Iodo-4-nitro-2-(1-methylheptyloxy)-aniline (44). The synthesis andphysical data of this compound are described elsewhere (WO 92/20058).

(S)-4-(1-Methylheptyloxy)-5-[(S)-5′-(1-methylheptyloxy)-2′-(hydroxy)-4′-(N,N-dimethylamino)-phenylazo]-2-nitro-1-iodobenzene(45). Compound 44 (300 mg, 0.77 mmol) was dissolved in 20 ml of a 15%concentrated HCl/ethanol solution and was then cooled to 0° C. with anice-salt water bath. To this solution, sodium nitrite (7.7 ml of a 0.1Msolution in water) was slowly added dropwise at a rate to maintain thetemperature at or below 2° C. (approximately 20 minutes). To this cooledsolution was added the dimethyl analine 43a (210 mg, 0.77 mmol)dissolved in 4 ml dichloromethane. Pyridine (2.4 ml) was slowly addeddropwise at a rate to maintain the temperature below 2° C.(approximately 20 minutes). An additional 15 ml dichloromethane wasadded to increase the solubility, the reaction mixture was stirred forone hour at 0° C. and then was allowed to warm to room temperature overan additional 30 minutes. The organic layer was separated and theaqueous portion was extracted with dichloromethane. The combined organiclayers were washed with 5% HCl, followed by brine and dried over MgSO₄.The crude product was adsorbed onto silica gel and purified via flashchromatography (80/20 hexanes/EtOAc). Evaporation of the solvent yielded360 mg (70%) of a metallic green solid.

(S)-[4″-(1-Methylheptyloxy)-5″-(N,N-dimethylamino)-2″-[(S)-2′″-(1-methylheptyloxy)-5′″-iodo-4′″-nitro-phenylazo]-phenyl]-4′-(decyloxy)-4-biphenylcarboxylate(46). The acid chloride 29 (373 mg, 1.0 mmol) dissolved in 5 mldichloromethane was added via syringe with stirring and under argon to asolution of the azo-dye (550 mg, 0.82 mmol), and triethylamine (100 mg,0.98 mmol) in 95 ml dichloromethane. The reaction mixture was stirred at25° C. for 16 hours and was then treated with 10% HCl. The organic layerwas separated, washed with brine and dried over MgSO₄. The crude productwas purified via flash chromatography over silica gel (90/10hexanes/EtOAc). Evaporation of the solvent yielded 535 mg (65%) of adark purple solid.

4-(Dodecyloxy)-4′-ethynyl-phenylbenzoate (47). The synthesis andphysical properties of this compound have been described elsewhere (WO92/20058).

Bis-Biphenylcarboxylate DR1 System

Example 1.10

(S)-[4″-(1-Methyl-heptyloxy)-5″-[(S)-5′″-(1-methyl-heptyloxy)-2′″-hydroxy-4′″-(N,N-dimethylamino)-phenylazo]-2″-nitro]-bis-(1″,2′″)-4′-(cis-9,cis-12-octadecadieneyloxy)-4-biphenylcarboxylate (W427). DCC (106 mg,0.51 mmol) dissolved in 1 ml dichloromethane was added, via syringe withstirring and under argon, to a solution of the carboxylic acid of 29c(190 mg, 0.41 mmol), 52a (115 mg, 0.20 mmol), and DMAP (13 mg, 0.10mmol) in 4 ml dichloromethane. The reaction mixture was stirredovernight at 25° C. and was then treated with 5% HCl. The organic layerwas separated and the aqueous layer was extracted with dichloromethane.The combined organic layers were washed with brine and dried over MgSO₄.TLC of the crude product showed mostly starting material, and NMRconfirmed that the major products were the mono-substituted azo dyes.The crude product was dissolved in dichloromethane (4 ml), and DMAP (13mg, 0.10 mmol) was added followed by triethylamine (40 mg, 0.40 mmol).The acid chloride of 29c (144 mg, 0.30 mmol) dissolved in 1 mldichloromethane was added via syringe with stirring and under argon. Thereaction mixture was stirred overnight at 25° C. and the previous workupwas repeated. The crude product was purified via flash chromatographyover silica gel with gradual elutions from 90/5/5 to 80/15/5 (v/v/v,Hex/EtOAc/dichloromethane). Evaporation of solvent yield 186 mg (31%) ofa dark red solid.

(S)-[4″-(1-Methyl-heptyloxy)-5″-[(S)-5′″-(1-methyl-heptyloxy)-2′″-hydroxy-4′″-(N,N-dimethyamino)-phenylazo]-2″-nitro]-bis-(1″,2′″)-4′-(decyloxy)-4-biphenylcarboxylate(W429). 4′-(decyloxy)-4-biphenyl-acid chloride (140 mg, 0.376 mmol)dissolved in 1.5 ml dichloromethane was added via syringe, with stirringand under argon, to a solution of 52a (100 mg, 0.179 mmol),triethylamine (45 mg, 0.448 mmol), and DMAP (11 mg, 0.09 mmol) in 2.5 mldichloromethane. The reaction mixture was stirred overnight at 25° C.and was then treated with 5% HCl. Dichloromethane (approximately 20 ml)was added, the organic layer was separated and washed with saturatedsodium bicarbonate, followed by brine, and dried over MgSO₄. The crudeproduct was adsorbed onto silica gel and purified via flashchromatography with gradual elutions from 90/5/5 to 80/15/5(hexanes/ethyl acetate/dichloromethane). Evaporation of the solventyielded 173 mg (79%) of a dark red solid.

(S)-[4″-(1-Methyl-heptyloxy)-5″-[5′″-(heptyloxy)-2′″-hydroxy-4′″-(N,N-dimethylamino)-phenylazo]-2″-nitro]-bis-(1″,2′″)-4′-(cis-9,cis-12-octadecadieneyloxy)-4-biphenylcarboxylate (W438). DCC (174 mg,0.84 mmol) dissolved in 0.5 ml dry THF was carefully added via syringe,with stirring and under argon, to a solution of azo-dye 52b (184 mg,0.338 mmol), carboxylic acid 29c (343 mg, 0.74 mmol), and DMAP (25 mg,0.20 mmol) in 3 ml dry THF. The reaction mixture was stirred overnightand then was treated with 5% HCl, and extracted with dichloromethane.The organic layer was washed with brine and dried over MgSO₄. The crudeproduct was adsorbed onto silica gel and purified via flashchromatography with gradual elutions from 90/5/5 to 75/20/5(hexanes/ethyl acetate/dichloromethane). Evaporation of solvent yielded278 mg (57%) of a dark red solid. This was then precipitated fromhexanes.

[4″-(Heptyloxy)-5″-[(S)-5′″-(1-methyl-heptyloxy)-2′″-hydroxy-4′″-(N,N-dimethylamino)-phenylazo]-2″-nitro]-bis-(1″,2′″)-4′-(cis-9,cis-12-octadecadieneyloxy)-4biphenylcarboxylate (W439). DCC (213 mg,1.03 mmol) dissolved in 1 ml dry THF was carefully added via syringe,with stirring and under argon, to a solution of azo-dye 52c (225 mg,0.413 mmol), carboxylic acid 29c (420 mg, 0.91 mmol), and DMAP (40 mg,0.33 mmol) in 5 ml dry THF. The reaction mixture was stirred for 48hours and then was treated with 5% HCl and extracted withdichloromethane. The organic layer was washed with brine and dried overMgSO₄. The crude product was adsorbed onto silica gel and purified viaflash chromatography with gradual elutions from 9015/5 to 75/20/5(hexanes/ethyl acetate/dichloromethane). Evaporation of solvent yielded277 mg (47%) of a dark red solid. This was then precipitated fromhexanes.

Bis-Phenol DR1 Fragment

(S)4-(1-Methylheptyloxy)-3-amino-phenylbenzoate (48a). Compound 32a(1.195 g, 3.22 mmol) was dissolved in ethanol (32 ml), and a small scoopof 10% Pd/C was added. The reaction flask was evacuated and filled withhydrogen three times. The reaction mixture was stirred under hydrogen(balloon) atmosphere overnight and then was filtered through a pad ofcelite. Evaporation of solvent yielded 1.10 g (100%) of a viscous brownoil. The crude product was used without further purification.

4-(Heptyloxy)-3-amino-phenylbenzoate (48b). A small scoop of 10% Pd/Ccatalyst was added to a solution of 32b (1.744 g, 4.88 mmol) in50 mlethanol. The flask was evacuated and filled with hydrogen three times.The reaction mixture was stirred overnight under hydrogen balloonatmosphere, then filtered through a pad of celite. Evaporation ofsolvent yielded 1.523 g (95%) of a brown solid.

(S)-4-(1-Methyl-heptyloxy)-3-(N-acetyl)amino-phenylbenzoate (49a).Acetyl chloride (1.04 ml, 14.6 mmol) was carefully added to a stirredsolution of 48a (500 mg, 1.46 mmol) in 15 ml ethyl acetate, and 30 ml ofa 10% aqueous Na₂CO₃ solution. The reaction mixture was stirred for 20minutes and then an additional 1.04 ml of acetyl chloride was added. Thereaction mixture was stirred for two hours, the organic layer was thenseparated, washed with brine, and dried over MgSO₄. Evaporation of thesolvent yielded 538 mg (96%) of a red-brown viscous oil. The crudeproduct was used without purification.

4-(heptyloxy)-3-(N-acetyl)amino-phenylbenzoate (49b). Acetyl chloride(2.11 ml, 29.6 mmol) was slowly added to a stirred solution of 48b in 30ml ethyl acetate and 60 ml of a 10% aqueous sodium carbonate solution.The reaction mixture was stirred for 30 minutes and then an additional2.1 ml of acetyl chloride was added. Stirring was continued for onehour, the organic layer was then separated, washed with brine, and driedover MgSO₄. Evaporation of solvent yielded 937 mg (86%) of an orangesolid. The crude product was used without purification.

(S)-4-(1-Methylheptyloxy)-5-(N-acetyl)amino-2-nitro-phenylbenzoate(50a). A solution of concentrated nitric acid (0.47 ml) and glacialacetic acid (2.6 ml) was carefully added at 0° C. to a stirred solutionof 49a (300 mg, 0.78 mmol) in 16 ml glacial acetic acid and 0.7 mlconcentrated sulfuric acid. The reaction mixture was stirred for 20minutes as it warmed to room temperature. Water (approximately 100 ml)was added and the reaction mixture was extracted twice withdichloromethane. The combined organic layers were washed with brine anddried over MgSO₄. Evaporation of the solvent yielded 294 mg (88%) of ayellow solid. The crude product was used without purification.

4-(Heptyloxy)-5-(N-acetyl)amino-2-nitro-phenylbenzoate (50b). A solutionof concentrated nitric acid (1.45 ml) and glacial acetic acid (8 ml) wasslowly added at 5-10° C. to a stirred solution of 49b (893 mg, 2.42mmol) in 50 ml glacial acetic acid. The reaction mixture was allowed towarm to room temperature over a 30 minute period. Water was then added,and the solution was extracted with dichloromethane. The organic layerwas washed with brine and dried over MgSO₄. Evaporation of solventyielded 893 mg (89%) of an orange solid. The crude product was usedwithout purification.

(S)-4-(1-Methylheptyloxy)-2-nitro-5-aminophenol (51a). Sodium hydroxide(687 mg, 17.2 mmol) was carefully added to a stirred solution of 50a(294 mg, 0.69 mmol), water (8 ml), and ethanol (25 ml). The reactionmixture was stirred overnight at 25° C. and then was neutralized withconcentrated HCl. The resulting solution was extracted twice withdichloromethane, and the combined organic layers were washed with brineand dried over MgSO₄. The crude product was concentrated and purifiedvia flash chromatography over silica gel with gradual elutions from90/10 to 80/20 (v/v, Hex/EtOAc). Evaporation of the solvent yielded 164mg (84%) of an orange oil which eventually solidified.

4-(Heptyloxy)-2-nitro-5-aminophenol (51b). Sodium hydroxide (2.15 g,53.7mmol) was carefully added to a stirred solution of 50b (890 mg, 2.15mmol) in 80 ml ethanol and 20 ml water. The reaction mixture was stirredovernight and was then acidified with concentrated HCl. Extracted threetimes with dichloromethane, and the combined organic layers were washedwith brine and dried over MgSO₄. The crude product was adsorbed ontosilica gel and purified via flash chromatography with gradual elutionsfrom 85/10/5 to 75/20/5 (Hex/EtOAc/dichloromethane). Evaporation ofsolvent yielded 469 mg (81%) of an orange solid.

(S)-4-(1-Methylheptyloxy)-5-[(S)-5′-(1-methylheptyloxy)-2′-hydroxy-4′-(N,N-dimethylamino)-phenylazo]-2-nitrophenol(52a). The amino-nitro compound 51a (357 mg, 1.26 mmol) was dissolved in33 ml of a 15% concentrated HCl in ethanol solution and was then cooledto 0° C. with an ice-salt bath. To this solution, sodium nitrite (12.5ml of a 0.1M solution in water) was slowly added dropwise at a rate tomaintain the temperature at or below 2° C. (approximately 20 minutes).To this cooled solution was added the dimethyl analine 43a (336 mg, 1.26mmol) dissolved in 5 ml dichloromethane. Pyridine (3.9 ml) was thenslowly added to the solution dropwise at a rate to maintain thetemperature below 2° C. (approximately 20 minutes). An additional 15 mlof dichloromethane was added to increase the solubility, the reactionmixture was stirred for one hour at 0° C. and was then allowed to warmto room temperature over an additional 30 minutes. The organic layer wasseparated, and the aqueous portion was extracted with dichloromethane.The combined organic layers were washed with 5% HCl, followed by brine,and dried over MgSO₄. The crude product was adsorbed onto silica gel andpurified via flash chromatography with gradual elutions from 85/10/5 to75/20/5 percentage of (Hex/EtOAc/dichloromethane). Evaporation of thesolvent yielded 635 mg (90%) of a metallic green solid.

(S)-4-(1-Methylheptyloxy)-5-[5′-(heptyloxy)-2′-hydroxy-4′-(N,N-dimethylamino)-phenylazo]-2-nitrophenol(52b). Compound 43b (143 mg, 0.57 mol), compound 51a (161 mg, 0.57mmol), 0.1M aqueous sodium nitrite (5.6 ml), and pyridine (1.8 ml) in 15ml of a 15% HCl/ethanol solution were reacted according to the procedurefor compound 52a. The crude product was adsorbed onto silica gel andpurified via flash chromatography with gradual elutions from 85/10/5 to75/20/5 (Hex/EtOAc/dichloromethane). Evaporation of solvent yielded 199mg (64%) of a metallic green solid.

4-(Heptyloxy)-5-[(S)-5′-(1-methylheptyloxy)-2′-hydroxy-4′-(N,N-dimethylamino)-phenylazo]-2-nitrophenol(52c). Compound 43a (388 mg, 1.46 mmol), compound 51b (392 mg, 1.46mmol), 0.1M aqueous sodium nitrite (14.5 ml), and pyridine (4.5 ml) in39 ml of a 15% HCl/ethanol solution were reacted according to theprocedure for compound 52a. The crude product was adsorbed onto silicagel and purified via flash chromatography with gradual elutions. from90/5/5 to 75/20/5 (Hex/EtOAc/dichloromethane). Recrystallization fromhexanes yielded 370 mg (46%) of a metallic green solid.

para-Nitroanalines

(S)-[4″-(1-Methylheptyloxy)-2″-(N,N-dimethylamino)-5″-nitrophenyl]-4′-decyloxy-4-biphenylcarboxylate(W450). DCC (110 mg, 0.53 mmol) dissolved in 1 ml dichloromethane wasadded via syringe, with stirring and under argon, to a solution ofphenol 60 (150 mg, 0.48 mmol) carboxylic acid 29 (171 mg, 0.48 mmol),and DMAP (24 mg, 0.19 mmol) in 9 ml dichloromethane. The reactionmixture was stirred for 24 hours and was then treated with 5% HCl. Theorganic layer was separated, washed with brine, and dried over MgSO₄.The crude product was purified via flash chromatography over silica gelwith gradual elutions from 98/2-80/20 (v/v, Hex/EtOAc). Evaporation ofsolvent yielded 141 mg (45%) of a yellow solid which was thenprecipitated from hexanes.

(S)-[4″-(1-Methylheptyloxy)-5″-(N,N-dimethylamino)-2″-nitrophenyl]-4′-decyloxy-4-biphenylcarboxylate(W451). The acid chloride of compound 29 (120 mg, 0.32 mmol), dissolvedin 1 ml dichloromethane, was added via syringe, with stirring and underargon, to a solution of phenol 61 (100 mg, 0.32 mmol) and triethyl amine(39 mg, 0.39 mmol) in 5 ml dichloromethane. The reaction mixture wasstirred overnight and was then treated with 5% HCl. Extracted withdichloromethane, the organic layer was washed with brine and dried overMgSO₄. The crude product was-purified via flash chromatography oversilica gel by elution with 15% dichloromethane and 85% (by volume) of a95/5, v/v, Hex/EtOAc solution. Evaporation of solvent yielded 146 mg(70%) of a yellow solid which was then precipitated from hexanes.

PNA Intermediates

4-(Benzyloxy)-3-nitro-phenylbenzoate (53). Benzyl chloride (5.35 ml,46.5 mmol) was added to a stirred solution of 31 (6.023 g, 23.2 mmol),potassium carbonate (6.428 g, 46.5 mmol), and potassium iodide (7.72 g,46.5 mmol) in 100 ml DMF. The reaction mixture was stirred for 24 hoursand then water was added (approximately 50 ml). Extracted twice withethyl acetate, and the combined organic layers were washed with 5% HCl,followed by brine, and dried over MgSO₄. The crude product wasrecrystallized from ethanol to yield 7.245 g (89%) of a yellow solid.

4-(Benzyloxy)-3-nitrophenol (54). Lithium hydroxide monohydrate (5.632g, 134.2 mmol) was added to a stirred solution of compound 53 (2.343 g,6.71 mmol) in 150 ml methanol and 50 ml water. THF (50 ml) was addedafter 20 minutes to increase solubility. The reaction mixture wasstirred overnight and was then acidified with concentrated HCl. Thereaction mixture was extracted five times with dichloromethane, and thecombined organic layers were washed with brine and dried over MgSO₄. Thecrude product was purified via flash chromatography over silica gel withgradual elutions from 80/10-50/50 (Hex/EtOAc). Evaporation of solventyielded 1.567 g (95%) of a yellow solid.

(S)-4-(1-Methylheptyloxy)-2-(nitro)-1-(benzyloxy)-benzene (55). DEAD(777 mg, 4.46 mmol), TPP (1.171 g, 4.46 mmol), R-2-octanol (511 mg, 3.93mmol), and compound 54 (875 mg, 3.57 mmol) were reacted according to theprocedure for compound 32a. The crude product was purified via flashchromatography over silica gel with gradual elutions from 95/5-80/20(Hex/EtOAc). Evaporation of solvent yielded 972 mg (76%) of a lightyellow oil.

(S)-4-(1-Methylheptyloxy)-2-aminophenol (56). A small scoop of Pearlmanscatalyst (Pd(OH)₂/C) was added to a solution of compound 55 (1.0 g, 2.8mmol) in 30 ml ethanol. The flask was evacuated, filled with hydrogenthree times, and stirred overnight under an H₂ balloon atmosphere. Thereaction mixture was filtered through a pad of celite, and evaporationof solvent yielded 639 mg (95%) of a tan solid. The crude product wasused without purification.

(S)-4-(1-Methylheptyloxy)-2-(N,N-dimethylamino)-phenol (57) [Borch, R.F. and Hassid, A., J. Org. Chem. (1972) 37:1673]. Sodiumcyanoborohydride (795 mg, 12.6 mmol) was carefully added at 0° C. to asolution of compound 56 (1.0 g, 4.2 mmol) and 37% aqueous formaldehyde(5.05 ml, 63.2 mmol) in 45 ml acetonitrile. The reaction mixture wasstirred for 5 minutes and then 0.4 ml glacial acetic acid was added. Thereaction mixture was stirred for one hour at room temperature and thenan additional 0.4 ml glacial acetic acid was added. The reaction mixturewas stirred for an additional one hour and then excess solvent wasevaporated off. The crude product was taken up in ether and treated with1N KOH. The reaction mixture was then acidified (pH=5) with concentratedHCl. The reaction mixture was extracted with ether, and the organiclayer was washed with brine and dried over MgSO₄. Evaporation of solventyielded 1.053 g (94%) of a red oil. The crude product was used withoutpurification.

(S)-4-(1-Methylheptyloxy)-2-(N,N-dimethylamino)-phenylacetate (58).Acetyl chloride (0.31 ml, 4.3 mmol) was carefully added to a stirredsolution of compound 57 (1.05 g, 3.96 mmol) and triethylamine (481 mg,4.75 mmol) in 40 ml dichloromethane. The reaction mixture was stirredfor 15 minutes and was then treated with 5% HCl. The organic layer wasseparated, washed with brine, and dried over MgSO₄. Evaporation ofsolvent yielded 1.069 g (88%) of an orange-red oil. The crude productwas used without purification.

(S)-4-(1-Methylheptyloxy)-2-(N,N-dimethylamino)-5-nitro-phenylacetate(59). Concentrated nitric acid (0.25 ml) was slowly added at 0° C. to astirred solution of compound 58 in 15 ml glacial acetic acid. Thereaction mixture was stirred for five minutes and was then diluted withwater. The reaction mixture was extracted with dichloromethane, theorganic layer was washed with brine and dried over MgSO₄. The crudeproduct was purified via flash chromatography over silica gel withgradual elutions from 90/10-50/50 (v/v, Hex/EtOAc). Evaporation ofsolvent yielded 188 mg (57%) of a viscous orange oil.

(S)-4(1-Methylheptyloxy)-2-(N,N-dimethylamino)-5-nitro-phenol (60).Lithium hydroxide monohydrate (226 mg, 5.38 mmol) was added to a stirredsolution of compound 59 in 15 ml THF and 5 ml water. The reactionmixture was stirred for 15 minutes and was then acidified withconcentrated HCl. Extracted with ether, the organic layer was washedwith brine and dried over MgSO₄. The crude product was purified viaflash chromatography over silica gel (80/20, v/v, Hex/EtOAc).Evaporation of solvent yielded 308 mg (92%) of a viscous orange oil.This product rapidly decomposes in chloroform and should be carried onimmediately to the next step.

(S)-4-(1-Methylheptyloxy)-5-(N,N-dimethylamino)-2-nitro-phenol (61).Concentrated nitric acid (0.20 ml) was added at 0° C. to a stirredsolution of compound 43a in 15 ml glacial acetic acid. The reactionmixture was stirred for 30 seconds until the solution turned dark red.The reaction mixture was then diluted with water and extracted threetimes with dichloromethane. The combined organic layers were washed withbrine and dried over MgSO₄. The crude product was purified via flashchromatography over silica gel with gradual elutions from 95/5-90/10(Hex/EtOAc). Evaporation of solvent yielded 103 mg (61%) of a viscousyellow oil.

Bis-PNA-Biphenylcarboxylate System

(S,R)-[2″-(N,N-Dimethylamino)-4″-(1-methylheptyloxy)-5″-nitrophenyl]-2′-(nitro)-4′-(1-methylheptyloxy)-5′-(N,N-dimethylamino)-4-biphenylcarboxylate(W454). DCC (54 mg, 0.26 mmol), carboxylic acid 65 (73 mg, 0.176 mmol),phenol 60 (120 mg, 0.387 mmol), and DMAP (9 mg, 0.07 mmol) in 8 mldichloromethane were reacted according to the procedure for compound 16.The crude product was purified via flash chromatography over silica gelwith gradual elutions from 90/10-50/50 (Hex/EtOAc). Evaporation ofsolvent yielded 72 mg (58%) of a yellow solid which was thenprecipitated from hexanes.

PNA Biphenylcarboxylic Acid Fragment

(R)-Methyl-3′-(amino)-4′-(1-methylheptyloxy)-4-biphenylcarboxylate (62).A small scoop of 10% Pd/C catalyst was added to a solution of 41c in 15ml methanol. The flask was evacuated and filled with hydrogen threetime. The reaction mixture was stirred three hours under H₂ balloonatmosphere and filtered through a pad of celite. Evaporation of solventyielded 169 mg (100%) of a gray solid. The crude product was usedwithout purification.

(R)-Methyl-3′-(N,N-dimethylamino)-4′-(1-methylheptyloxy)-4-biphenylcarboxylate(63). Sodium cyanoborohydride (202 mg, 3.20 mmol), compound 62 (380 mg,1.07 mmol), glacial acetic acid (2×0.09 ml), and aqueous formaldehyde(1.28 ml, 16.0 mmol) in 35 ml acetonitrile were reacted according to theprocedure for compound 57. Evaporation of solvent yielded 321 mg (78%)of a white solid. The crude product was used without purification.

(R)-Methyl-2′-(nitro)-4′-(1-methylheptyloxy)-5′-(N,N-dimethylamino)-4-biphenylcarboxylate(64). Acetic anhydride (3 drops) was added to a stirred solution ofcompound 63 (75 mg, 0.195 mmol), sodium nitrate (17 mg, 0.205 mmol),water (0.3 ml), concentrated HCl (0.16 ml), dichloromethane (0.5 ml),and ether (3 ml). The reaction mixture was stirred for 15 minutes andthen more HCl and Ac₂O were added until the solution changed color to abright yellow. After the color had changed, the reaction mixture wasstirred for an additional three hours, and then the organic layer wasseparated, washed with brine, and dried over MgSO₄. The crude productwas purified via flash chromatography over silica gel with gradualelutions from 95/5-80/20 (Hex/EtOAc). Evaporation of solvent yielded 36mg (43%) of a yellow solid.

(R)-2′-(Nitro)-4′-(1-Methylheptyloxy)-5′-(N,N-dimethylamino)-4-biphenylcarboxylicacid (65). Lithium hydroxide monohydrate (96 mg, 2.28 mmol) was added toa stirred solution of compound 64 (49 mg, 0.11 mmol), THF (2 ml), water(3 ml), and methanol (10 ml). The reaction mixture was refluxedovernight and then was acidified with concentrated HCl. The reactionmixture was extracted twice with dichloromethane, the combined organiclayers were washed with brine and dried over MgSO₄. Evaporation ofsolvent yielded 47 mg (100%) of a yellow solid. The crude product wascarried on without purification.

Example 1.11

The following reaction schemes illustrate and compare the methods forpreparation of stilbene derivatives (122 and 140) in which the NO₂ groupis meta (122) or ortho (140) to the chiral tail or:

Example 1.12

This example illustrates additional methods for preparation of compoundsof this invention. Compound MDW 1115 (153) its analogs and relatedcompounds can be prepared by the reaction of the following scheme:

Hexyl 2-Bromo-3-hydroxycinnamate 143. To 2 g (12.2. mmoles) ofhydroxycinnamic acid 141 in 60 ml glacial acetic acid was added,dropwise, a solution of 1.85 g (11.6 mmoles) bromine in 5 ml glacialacetic acid. When all the bromine had been added, the acetic acid wasdistilled off, leaving behind bromoacid 142 as a white melt. To thismelt was then. added 22 ml hexanol and 50 mg toluenesulfonic acid. Thehexanol-water azeotrope (bp. 100° C.) was distilled off dropwise atambient pressure, until only about half the hexanol remained, and theremainder of the hexanol was then removed in vacuo. The reaction mixturewas chromotographed on silica gel using 15% ethyl acetate in haxanes toyield 0.77 g (20%) of bromoester 143 as a white solid.

(trans-4-Pentyl)cyclohexylmethanol 145. To a flask containing 1.91 g (50mmoles) lithium aluminum hydride and 50 mL ether, cooled to 0° C., wasadded 5 g (25 mmoles) acid 144. The reaction was warmed to roomtemperature and allowed to stir overnight, at which time it was againcooled to 0° C. and a reflux condenser was attached. Water (1.91 mL),15% sodium hydroxide (1.91 mL), and water (5.73 mL) were then addeddropwise. When the suspension was white, magnesium sulfate was added asa drying agent, and the solution was filtered. The solvent was removedin vacuo to yield 4.24. g (91%) of alcohol 145.

(trans-4-Pentyl)cyclohexylmethanol toluenesulfonate 146. To a flaskcontaining 4.24 g (23 mmoles) alcohol 145 was added 5.47 g (24 mmoles)toluenesulfonyl chloride and 7 mL anhydrous tetrahydrofuran. Thereaction mixture was cooled in an ice bath and 4.6 mL (57 mmoles)pyridine was added. the reaction mixture was stirred 30 min., thenallowed to stand at −20° C. for 12 hours. It was then poured into a 10%HCl solution and extracted with 1:1 ethyl acetate:hexane. The solventwas removed in vacuo and the residue was dissolved in tetrahydrofuran.Triethylamine 94 mL) and about 8 drops water were added, and the mixturewas allowed to stir for 1 hour. The mixture was checked by TLC (9:1hexane:ethyl acetate) for remaining tosyl chloride; if any remained,additional drops of water were added and the mixture was stirred foranother hour. When no tosyl chloride remained, it was then poured into a10% HCl solution and extracted with 1:1 ethyl acetate:hexane. Thecombined organic layers were washed with saturated sodium chloride(brine), then dried over magnesium sulfate. The solvent was removed invacuo to give 7.8 g (100%) of tosylate 146 as a slightly yellow solid.

Octyl 3-bromo-4-((trans-4-pentyl)cyclohexylmethyleneoxy)cinnamate 147.To a flask containing 300 mg (0.92 mmoles) bromophenol 143 was added 341mg (1.01 mmoles) tosylate 146,388 mg (1.2 mmoles) anhydrous cesiumcarbonate, and 1.83 mL anhydrous dimethylformamide. The solution washeated to 100° C. and allowed to stir for 1 hour. It was then cooled toroom temperature, poured into a solution of 10% HCl, and extracted with1:1 hexane:ethyl acetate. The combined organic layers were washed withbrine and dried over magnesium sulfate, and the solvent was removed invacuo. The product was chromatographed on silica gel using 5% ethylacetate in hexane (product Rf 0.24) to give 139 mg (30%) of the ether147 as a white solid.

2-Bromo-4-(trans-4-pentylcyclohexyl)ethylene)phenol 149. To a flaskcontaining 5 g (18 mmoles) 4-((trans-4-pentylcyclohexyl)ethylene)phenol148 was added 90 mL glacial acetic acid. Into a small flask was weighed2.60 g (16.3 mmoles) bromine, and to this was added 5 mL glacial aceticacid. This solution was added dropwise to the reaction mixture, ensuringthat the color of the mixture did not go past yellow-orange. The mixturewas stirred an additional hour, then poured into water and ethylacetate. The organic layer was washed three times with water, then twicewith saturated sodium bicarbonate, and finally with brine. The organiclayer was dried over sodium sulfate, and the solvent was removed invacuo. The product was chromatographed on silica gel with 5% ethylacetate in hexanes to yield 5.39 g (94% based on bromine) of bromophenol149 as a white solid.

2-Bromo-4-((trans-4-pentylcyclohexyl)ethylene)phenoxy4′-octyloxybenzoate 150. To a flask containing 1.22 g (4.88 mmoles)4-octyloxybenzoic acid was added 1.2 mL oxalyl chloride. The reactionmixture was stirred one hour, and then the excess oxalyl chloride wasremoved in vacuo. To this flask was added phenol 149 and 13 mL anhydroustetrahydrofuran. The mixture was stirred until homogenous, then 2.96 mL(21 mmoles) freshly distilled dry triethylamine were added the mixturewas allowed to stir 12 hours, then was poured into a solution of 10%HCl, and extracted with 1:1 hexane:ethyl acetate. The combined organiclayers were washed with brine and dried over magnesium sulfate, and thesolvent was removed in vacuo. The product was chromatographed on silicagel using 5% ethyl acetate in hexane to give 2.16 g (87%) of ester 150as a white solid.

2-Trimethylsilylacetyleneyl-4-((trans-4-penylcyclohexyl)ethylene)phenoxy4′-octyloxybenzoate 151. To a flask containing 1.5 g (2.56 mmoles) ofphenyl bromide 150 was added 0.54 mL (3.8 mmoles)trimethylsilylacetylene. 298 mg (0.26 mmoles)tetrakis(triphenylphosphine)palladium, and 13 mL triethylamine. Drynitrogen was bubbled through the solution for 20 minutes, and it wasthen refluxed for 18 hours. The black reaction mixture was passedthrough 3 cm of silica gel, eluting with 10% ethyl acetate in hexanes.The product was chromatographed on silica gel using 5% ethyl acetate inhexanes to give 0.70 g (45%) of the alkyne 151 as a white solid.

2-Acetylenyl4-((trans-4-pentylcyclohexyl)ethylene)phenoxy4′-octyloxybenzoate 152. To a flask containing 0.94 g (1.56 mmoles) ofsilane 151 in 5 mL tetrahydrofuran was added 130 mg (1.56 mmoles) sodiumbicarbonate and 3.1 mL (3.1 mmoles) of a 1 M solution oftetrybutylammonium fluoride in tetrahydrofuran. The reaction mixtureimmediately turned red. It was allowed to stir 15 minutes, at which timeit was poured into water and extracted with 1:1 ethyl acetate:hexane.The combined organic layers were washed with brine and dried overmagnesium sulfate, and the solvent was removed in vacuo. The product waschromatographed on silica gel using 3% ethyl acetate in hexane to give400 mg (48%) of acetylene 152 as a white solid.

5-(trans-4′″-Pentylcylohexyl)ethylene)-2-(4″-Octyloxyphenylcarbonyloxy)-5′-(hexyloxycarbonylvinyl)-2′-(trans-4″″-pentyl)cyclohexylmethyleneoxy)tolane153. To a flask containing 139 mg (0.27 mmoles) of aryl bromide 147 and145 mg (0.27 mmoles) acetylene 152 was added 32 mg (0.027 mmoles)tetrakis(triphenylphosphine)palladium and 2 ml diisopropylamine. Drynitrogen was bubbled through the solution for 15 minutes, and it wasthen refluxed for 18 hours. The cooled reaction mixture was filteredthrough 3 cm silica gel using 10% ethyl acetate in hexane a the eluent.The product was then chromatographed on silica gel using 5% ethylacetate in hexane to yield 112 mg of the dimer 153. This product wasrecrystallized from a solution of hexane, ethyl acetate, andacetonitrile to give 78 mg (30%) of a slightly yellow solid.

Specific examples of negative birefringement materials that can be madeby this method or routine adaptations of this method include MDW 1115 aswell as its derivatives 1115A and B illustrated below and MDW 1069 andits derivatives MDW 1069A and B (phase diagrams are given for MDW 1115and MDW 1115:

where X, Z, x, z, R³, R⁴, R⁵ and R⁶ are as defed in formula I, W₁ andW₂, independently of one another, can be —O— or a —CH₂— group and R′ andR″, independently of one another, can be groups as defined for R¹ andR². Preferred R′ and R″ are groups having 1 to about 6 carbon atoms. MDW1069 has structure VII where x and z are O, R⁵ and R⁶ are H, W₁ and W₂are —CH₂—, R³ and R⁴ are —C₈H₁₇, R′ and R″ are both C₅H₁₁ and has thephase diagram:

I—(198° C.)→C--(116° C.)→X←(130° C.)—

MDW 1115 has structure VII where x and z are O, R⁵ and R⁶ are H, W₁ is—CH₂—, W₂ is O, R³ is C₈H₁₇,R⁴ is —C₆H₁₃, R′ and R″ are both C₅H₁₁ andhas the phase diagram:

I—(>200° C. )→A--(300° C.)→X←(84° C.)—

Other compounds od formula VII that are of interest in this inventionare those in which one or both of the groups —[X]_(x)—R⁵ and —[Z]_(z)—R⁶are —C≡C—H or —C≡C—R⁵, or —C≡C—R⁶ with preferred R⁵ and R⁶ being alkylor haloalkyl having 1 to about 6 carbon atoms. Of particular interestare those compounds of formula VII where one or both of —[X]_(x)—R⁵ and—[Z]_(z)—R⁶ are —C≡C—CH₃. FIG. 5 illustrates negative birefringence ofMDW 1069 in the visible region.

The specific examples provided herein are illustrative and in no wayintended to limit the scope of the invention which is defined by theappended claims.

All of the references cited in this specification are incorporatedherein in their entirety by reference.

We claim:
 1. A liquid crystal composition exhibiting anomalousbirefringence and comprising a rod-like liquid crystal compound whichexhibits negative birefringence wherein the liquid crystal compound isnot a polymer.
 2. The liquid crystal composition of claim 1 wherein theliquid crystal compound comprises liquid crystal monomers linked througha high birefringence moiety.
 3. The liquid crystal composition of claim1 that is a ferroelectric LC composition.
 4. An electrooptical devicewhich employs the composition of claim
 1. 5. The electrooptical deviceof claim 4 which is achromatic.
 6. An electrooptical display deviceexhibiting true colors which employs a liquid crystal composition ofclaim
 1. 7. The liquid crystal composition of claim 1 which exhibitszero birefringence.
 8. The liquid crystal composition of claim 7 whichexhibits a nematic phase.
 9. The liquid crystal composition of claim 7which exhibits a smectic phase.
 10. The liquid crystal composition ofclaim 9 that is a ferroelectric liquid crystal composition.
 11. Anelectrooptical device which employs the composition of claim
 7. 12. Theelectrooptical device of claim 11 which is achromatic.
 13. Theelectrooptical device of claim 11 which exhibits true colors.
 14. Aliquid crystal composition exhibiting anomolous birefringence andcomprising a rod-like liquid crystal dimer molecule exhibiting negativebirefringence.
 15. An electrooptical device which employs the liquidcrystal composition of claim
 14. 16. A liquid crystal compoundexhibiting negative birefringence which is a dimer.
 17. The liquidcrystal compound of claim 16 wherein the dimer comprises liquid crystalmonomers linked through a high birefringence moiety.
 18. The liquidcrystal compound of claim 17 comprising a core and one or two tailportions wherein the majority of the pi-electron delocalization of thecore is along the extraordinary axis of the liquid crystal compound. 19.A liquid crystal composition comprising a liquid crystal dimer of claim16.
 20. The liquid crystal composition of claim 19 wherein the liquidcrystal dimer comprises liquid crystal monomers linked through a highbirefringence moiety.
 21. The liquid crystal composition of claim 20wherein the dimer comprises a core and one or two tail portions whereinthe majority of the pi-electron delocalization of the core is along theextraordinary axis of the liquid crystal compound.
 22. The liquidcrystal composition of claim 21 wherein the one or two tail portionshave the formula: —[X]_(x)—R⁵ where: x, independently of x in othertails, is 0 or 1; X, independently of X in other tails, is selected fromthe group consisting of electron acceptor groups, electron donor groups,hydrogen, halogen, —NO₂, —C═C—, —C C—, —COO—, —OOC—, —CO—, O, S, —COS—,—SCO—, —CN, —NH—, —NR′—, where R′ is a small alkyl having 1 to about 3carbon atoms, —NHCO—, —NR′CO—, where R′ is a small alkyl having 1 toabout 3 carbon atoms, —SO—, and C—SO₂—; R⁵, independently of R⁵ in othertails, is selected from the group consisting of hydrogen, halogen, —CN,alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, and haloalkynyl groupshaving from 1 to about 20 carbon atoms, wherein one or morenon-neighboring —CH₂— groups in the substituent can be substituted withan oxygen, a sulfur, or a SiR^(A)R^(B) group, where R^(A) and R^(B) aresmall alkyl or alkenyl groups having from 1 to about 6 carbon atoms; andwhen X is present, R⁵ may be absent.
 23. The liquid crystal compositionof claim 22 wherein the liquid crystal core comprises aromatic rings andhas the formula:

wherein: a is 0 or 1; A is selected from the group consisting of a—C═C—, —C≡C—, —C≡C—C≡C—, —C═C—C═C—, —C≡C—C═C—C≡C—, —N═N—, —N═NO—, and a—HC═N— group; b₁-b₄, independently of one another, are 0 or 1; B₁-B₄,independently of one another, are selected from the group consisting of—C═C—, —C≡C—, —COO—, —OOC—, —CO—, —O—, —CH₂O—, —OCH₂—, —CH₂—CH₂—, —S—,—COS—, —SOC—, —CH═CHCOO—, —OOCCH═CH—, —CH═CHCOS—, and —SOCCH═CH—; c₁,and c₂, independently of one another, are 0 or 1 and C₁ and C₂,independently of one another, are selected from the group consisting of—C═C—, —C≡C—, —COO—, —OOC—, —CO—, —O—, —CH₂O—, —OCH₂—, —CH₂—CH₂—, —S—,—COS—, —SCO—, —CH═CHCOO—, —OOCCH═CH—, —CH═CHCOS— and —SOCH═CH—; d₁ andd₂, independently of one another, are 0 or 1; D₁ and D₂, independentlyof one another, are selected from the group consisting of —C═C—, —C≡C—,—COO—, —OOC—, —CO—, —O—, —CH₂O—, —OCH₂—, —CH₂—CH₂—, —S—, —COS—, —SOC—,—CH═CHCOO—, —OOCCH═CH—, —CH═CHCOS—, and —SOCCH═CH—; e₁ and e₂,independently of one another, are 0 or 1; E₁ and E₂, independently ofone another, are selected from the group consisting of —C═C—, —C≡C—,—COO—, —OOC—, —CO—, —O—, —CH₂O—, —OCH₂—, —CH₂—CH₂—, —S—, —COS—, —SOC—,—CH═CHCOO—, —OOCCH═CH—, —CH═CHCOS—, and —SOCCH═CH—; six-memberedaromatic rings E, F, G, H, I and J, independently of one another, are1,4-phenyl rings or 1,4-phenyl rings in which one or two of the carbonatoms of the ring are replaced with nitrogen atoms and in which carbonsof the phenyl rings or nitrogen-containing phenyl rings can besubstituted with halogens, —CN, —NO₂ or small alkyl, alkenyl, alkynyl,haloalkyl, haloalkenyl or haloalkynyl groups having from 1 to about 3carbon atoms; Y₁-Y_(4,) substituents on rings E and F, independently ofone another, are selected from the group consisting of hydrogen,halogen, —CN, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, andhaloalkynyl groups having from 1 to about 20 carbon atoms, wherein oneor more non-neighboring —CH₂— groups in the substituent can besubstituted with an oxygen, a sulfur or a SiR^(A)R^(B) group, whereR^(A) and R^(B) are small alkyl or alkenyl groups having from 1 to about6 carbon atoms, with the proviso that any ring position of aromaticrings E or F that is a nitrogen is not substituted with any of theY₁-Y₄; X and Z, independently of one another, are selected from thegroup consisting of electron acceptor groups, electron donor groups,hydrogen, halogen, —NO₂, —C═C—, —C≡C—, —COO—, —OOC—, —CO—, —O—, —S—,—COS—, —SCO—, —CN, —NH—, —NR′—, where R′ is a small alkyl having 1 toabout 3 carbon atom, —NHCO—, —NR′CO—, where R′ is a small alkyl having 1to about 3 carbon atoms, —SO—, and —SO₂—, with the proviso that any ringposition of aromatic rings E or F that is a nitrogen is not substitutedwith any X or Z, and R¹, R², R³, and R⁴, independently of one another,are selected from the group consisting of linear, branched or cyclicalkyl, alkenyl or alkynyl groups having from 1 to about 20 carbon atomswherein one or more —CH_(2—) groups can be optionally substituted withone or more halogens, or —CN groups, or in which one or morenon-neighboring —CH₂— groups can be replaced with an oxygen, a sulfur,or a substituted silyl group, Si(R^(A))(R^(B)), in which R^(A) andR^(B), independently, are alkyl, alkenyl, alkynyl, haloalkyl,haloalkenyl or haloalkynyl groups having from 1 to about 6 carbon atoms.24. An electrooptical device which comprises the liquid crystalcomposition of claim
 16. 25. The electrooptical device of claim 24 whichis achromatic.
 26. An electrooptical device which employs thecomposition of claim
 22. 27. The electrooptical device of claim 26 whichis achromatic.
 28. A liquid crystal composition comprising a compoundwhich exhibits negative birefringence and has the formula:

where: a is 0 or 1 and A is selected from the group consisting of a—C═C—, —C≡C—, —C≡C—C≡C—, —C═C—C═C—, —C≡C—C═C—C≡C—, —N═N—, —N═NO—, and a—HC═N— group; b₁-b₄, independently of one another, are 0 or 1 and B₁-B₄,independently of one another, are selected from the group consisting of—C═C—, —C≡C—, —COO—, —OOC—, —CO—, —O—, —CH₂O—, —OCH₂—, —CH₂—CH₂—, —S—,—COS—, —SOC—, —CH═CHCOO—, —OOCCH═CH—, —CH═CHCOS—, and —SOCCH═CH—; d₁ andd₂, independently of one another, are 0 or 1 and D₁ and D₂,independently of one another, are selected from the group consisting of—C═C—, —C≡C—, —COO—, —OOC—, —CO—, —O—, —CH₂O—, —OCH₂—, —CH₂—CH₂—, —S—,—COS—, —SOC—, —CH═CHCOO—, OOCCH═CH—, —CH═CHCOS—, and —SOCCH═CH—; e₁ ande₂, independently of one another, are 0 or 1 and E₁ and E₂,independently of one another, are selected from the group consisting of—C═C—, —C≡C—, —COO—, —OOC—, —CO—, —O—, —CH₂O—, —OCH₂—, —CH₂—CH₂—, —S—,—COS—, —SOC—, —CH═CHCOO—, —OOCCH═CH—, —CH═CHCOS—, and —SOCCH═CH—;six-membered aromatic rings E and F, independently of one another, arephenyl rings or phenyl rings in which one or two of the carbon atoms ofthe ring are replaced with nitrogen atoms and wherein the carbon atomsof the phenyl or nitrogen-containing phenyl rings can be substitutedwith a halogen, —CN, —NO₂, alkyl, alkenyl, alkynyl, haloalkyl,haloalkenyl; or haloalkynyl groups having from 1 to about 20 carbonatoms; Y₁-Y₄, substituents on rings E and F, independently of oneanother, are selected from the group consisting of hydrogen, halogen,—CN, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, and haloalkynylgroups having from 1 to about 20 carbon atoms, wherein one or morenon-neighboring —CH_(2—) groups in the substituent can be substitutedwith an oxygen, a sulfur, or a SiR^(A)R^(B) group, where R^(A) and R^(B)are small alkyl or alkenyl groups having from 1 to about 6 carbon atoms,with the proviso that any ring position of aromatic rings E or F that isa nitrogen is not substituted with any of the Y₁-Y₄; x and z,independently of one another are 0 or 1; X and Z, independently of oneanother, are selected from the group consisting of electron acceptorgroups, electron donor groups, hydrogen, halogen, —NO₂, —C═C—, —C≡C—,—COO—, —OOC—, —CO—, —O—, —S—, —COS—, —SCO—, —CN, —NH—, —NR′—, where R′is a small alkyl having 1 to about 3 carbon atom, —NHCO—, —NR′CO—, whereR′ is a small alkyl having 1 to about 3 carbon atoms, —SO—, and —SO₂—,with the proviso that any ring position of aromatic rings E or F that isa nitrogen is not substituted with any X or Z; R⁵ and R⁶, independentlyof one another, are selected from the group consisting of hydrogen,halogen, —CN, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, andhaloalkynyl groups having from 1 to about 20 carbon atoms, wherein oneor more non-neighboring —CH₂— groups in the substituent can besubstituted with an oxygen, a sulfur, or a SiR^(A)R^(B) group, whereR^(A) and R^(B) are small alkyl or alkenyl groups having from 1 to about6 carbon atoms, dependent upon the X or Z group, R⁵, R⁶ or both may beabsent; M₁-M₄, independently of one another, are core moieties havingfrom one to four aromatic or non-aromatic rings, optionally separated byup to three linking groups F₁-F₃ as in formula:—[N₁]_(n1)—[F₁]_(f1)—[N₂]_(n2)—[F₂]_(f2)—[N₃]_(n3)—[F₃]_(f3)—[N₄]_(n4)— where f1-f4, independently of one another, are 0 or 1, F₁-F₄,independently of one another, are selected from the group consisting of—C═C—, —C≡C—, —COO—, —OOC—, —CO—,—O—, —CH₂O—, —OCH₂—, —CH₂—CH₂—, —S—,—COS—, —SOC—, —CH═CHCOO—, —OOCCH═CH—, —CH═CHCOS—, and —SOCCH═CH—; andn1-n4, independently of one another, are 0 or 1, and N₁-N₄ are selectedfrom the group consisting of aromatic rings having one or two six-memberand/or five-membered aromatic rings, which may be fused or non-fusedring systems, or monocyclic or bicyclic alkyl and alkenyl non-aromaticrings having from 5 to about 12 ring carbon atoms wherein in each ringof N₁-N₄, one or more of the ring carbons can be substituted with ahalogen, —CN, small alkyl, alkenyl or alkynyl group having from 1 toabout 3 carbon atoms or small halogenated alkyl, halogenated alkenyl orhalogenated alkynyl in each ring of N₁-N₄ that is aromatic, one or twoof the ring carbons can be replaced with a nitrogen (N), in each ring ofN₁-N₄ that is non-aromatic, one or two non-neighboring —CH₂— groups canbe replaced with an oxygen; one of M₁-M₄ is absent; and R¹, R², R³, andR⁴, independently of one another, are selected from the group consistingof linear, branched or cyclic alkyl, alkenyl and alkynyl groups havingfrom 1 to about 20 carbon atoms, wherein one or more —CH_(2—) groups canbe optionally substituted with one or more halogens, or —CN groups, orin which one or more non-neighboring —CH₂— groups can be replaced withan oxygen, a sulfur, or a substituted silyl group, Si(R^(A))(R^(B)), inwhich R^(A) and R^(B), independently, are alkyl, alkenyl, alkynyl,haloalkyl, haloalkenyl or haloalkynyl groups having from 1 to about 6carbon atoms.
 29. An electrooptical device which comprises the liquidcrystal composition of claim
 28. 30. The electrooptical device of claim29 which is achromatic.
 31. The liquid crystal composition of claim 1wherein the liquid crystal compound which exhibits negativebirefringence has the formula:

where a is 0 or 1 and A is selected from the group consisting of a—C═C—, —C≡C—, —C≡C—C≡C—, —C═C—C═C—, —C≡C—C═C—C≡C—, —N═N—, —N═NO—, and a—HC═N— group; b₁-b₄, independently of one another, are 0 or 1 and B₁-B₄,independently of one another, are selected from the group consisting of—C═C—, —C≡C—, —COO—, —OOC—, —CO—, —O—, —CH₂O—, —OCH₂—, CH₂—CH₂—, —S—,—COS—, —SOC—, —CH≡CHCOO—, —OOCCH═CH—, —CH═CHCOS—, and —SOCCH═CH—; d₁ andd₂, independently of one another, are 0 or 1 and D₁ and D₂,independently of one another, are selected from the group consisting of—C═C—, —C≡C—, —COO—, —OOC—, —CO—, —O—, —CH₂O—, —OCH₂—, —CH₂—CH₂—, —S—,—COS—, —SOC—, —CH═CHCOO—, —OOCCH═CH—, —CH═CHCOS—, and —SOCCH═CH—; e₁ ande₂, independently of one another, are 0 or 1 and E₁ and E₂,independently of one another, are selected from the group consisting of—C═C—, —C≡C—, —COO—, —OOC—, —CO—, —O—, —CH₂O—, —OCH₂—, —CH₂—CH₂—, —S—,—COS—, —SOC—, —CH═CHCOO—, —OOCCH═CH—, —CH═CHCOS—, and —SOCCH═CH—;six-membered aromatic rings E and F, independently of one another, arephenyl rings or phenyl rings in which one or two of the carbon atoms ofthe ring are replaced with nitrogen atoms and wherein the carbon atomsof the phenyl or nitrogen-containing phenyl rings can be substitutedwith a halogen, —CN, —NO₂, alkyl, alkenyl, alkynyl, haloalkyl,haloalkenyl, or haloalkynyl groups having from 1 to about 20 carbonatoms; Y₁-Y₄, substituents on rings E and F, independently of oneanother, are selected from the group consisting of hydrogen, halogen,—CN, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, and haloalkynylgroups having from 1 to about 20 carbon atoms, wherein one or morenon-neighboring —CH₂— groups in the substituent can be substituted withan oxygen, a sulfur or with a SiR^(A)R^(B) group, where R^(A) and R^(B)are small alkyl or alkenyl groups having from 1 to about 6 carbon atoms,with the proviso that any ring position of aromatic rings E or F that isa nitrogen is not substituted with any of the Y₁-Y₄; x and z,independently of one another are 0 or 1; X and Z, independently of oneanother, are selected from the group consisting of electron acceptorgroups, electron donor groups, hydrogen, halogen, —NO₂, —C═C—, —C≡C—,—COO—, —OOC—, —CO—, —O—, —S—, —COS—, —SCO—, —CN, —NH—, —NR′—, where R′is a small alkyl having 1 to about 3 carbon atom, —NHCO—, —NR′CO—, whereR′ is a small alkyl having 1 to about 3 carbon atoms, —SO—, and —SO₂—,with the proviso that any ring position of aromatic rings E or F that isa nitrogen is not substituted with any X or Z, and R⁵ and R⁶,independently of one another, are selected from the group consisting ofhydrogen, halogen, —CN, alkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl,and haloalkynyl groups having from 1 to about 20 carbon atoms, whereinone or more non-neighboring —CH₂— groups in the substituent can besubstituted with an oxygen, a sulfur or with a SiR^(A)R^(B) group, whereR^(A) and R^(B) are small alkyl or alkenyl groups having from 1 to about6 carbon atoms, dependent upon the X or Z group, R⁵ and/or R⁶ may beabsent; M₁-M₄, independently of one another, are core moieties havingfrom one to four aromatic or non-aromatic rings, optionally separated byup to three linking groups F₁-F₃ as in formula:—[N₁]_(n1)—[F₁]_(f1)—[N₂]_(n2)—[F₂]_(f2)—[N₃]_(n3)—[F₃]_(f3)—[N₄]_(n4)— where f1-f4, independently of one another, are 0 or 1, F₁-F₄,independently of one another, are selected from the group consisting of—C═C—, —C≡C—, —COO—, —OOC—, —CO—, —O—, —CH₂O—, —OCH₂—, —CH₂—CH₂—, —S—,—COS—, —SOC—, —CH═CHCOO—, —OOCCH═CH—, —CH═CHCOS—, and —SOCCH═CH—; andn1-n4, independently of one another, are 0 or 1, and N₁-N₄ are selectedfrom the group consisting of aromatic rings having one or two six-memberand/or five-membered aromatic rings, which may be fused or non-fusedring systems, or monocyclic or bicyclic alkyl and alkenyl non-aromaticrings having from 5 to about 12 ring carbon atoms wherein in each ringof N₁-N₄, one or more of the ring carbons can be substituted with ahalogen, —CN, small alkyl, alkenyl or alkynyl group having from 1 toabout 3 carbon atoms or small halogenated alkyl, halogenated alkenyl orhalogenated alkynyl in each ring of N₁-N₄ that is aromatic, one or twoof the ring carbons can be replaced with a nitrogen (N), in each ring ofN₁-N₄ that is non-aromatic, one or two non-neighboring —CH₂— groups canbe replaced with an oxygen; any of M₁-M₄ can be absent; and R¹, R², R³,and R⁴, independently of one another, are selected from the groupconsisting of linear, branched or cyclic alkyl, alkenyl or alkynylgroups having from 1 to about 20 carbon atoms wherein one or more —CH₂—groups can be optionally substituted with one or more halogens, or —CNgroups, or in which one or more non-neighboring —CH₂— groups can bereplaced with an oxygen, a sulfur, or a substituted silyl group,Si(R^(A))(R^(B)), in which R^(A) and R^(B), independently, are alkylalkenyl, alkynyl, haloalkyl, haloalkenyl or haloalkynyl groups havingfrom 1 to about 6 carbon atoms.
 32. The liquid crystal composition ofclaim 31 wherein in the formula of the liquid crystal compound whichexhibits negative birefringence a is 1 and A is —N═N—.
 33. The liquidcrystal composition of claim 32 wherein the liquid crystal compound hasthe formula:

wherein a is 1, A is —N═N—, b₁ and b₂ are 1, c₁ and c₂ are 0, B₁ and B₂are —CO₂—, Y₁-Y₄ are all hydrogens, all of rings E, F, G, H, I and J arephenyl rings, and one of X or Z is —NO₂ and the other of X or Z is—NR′R⁵ where R′ is a small alkyl having 1 to about 3 carbon atom and R⁵is an alkyl group.
 34. The liquid crystal composition of claim 33wherein d₁, d₂, e₁ and e₂ are all 1 and D₁, D₂, E₁ and E₂ are all —O— inthe formula of the liquid crystal compound which exhibits negativebirefringence.
 35. The liquid crystal composition of claim 34 wherein R¹and R² are both chiral non-racemic alkyl groups in the formula of theliquid crystal compound which exhibits negative birefringence.
 36. Theliquid crystal composition of claim 35 wherein R³ and R⁴ are alkenegroups in the formula of the liquid crystal compound which exhibitsnegative birefringence.
 37. The liquid crystal composition of claim 36wherein R³ and R⁴ are dienes in the formula of the liquid crystalcompound which exhibits negative birefringence.
 38. The liquid crystalcomposition of claim 37 wherein R³ and R⁴ are both trans, trans—(CH₂)₈—CH═CH—CH₂—CH═CH—C₅H₁₁ groups in the formula of the liquidcrystal compound which exhibits negative birefringence.
 39. The liquidcrystal composition of claim 38 wherein R¹ and R² are both chiralnon-racemic —(CH₃)CH—C₆H₁₃ groups in the formula of the liquid crystalcompound which exhibits negative birefringence.
 40. The liquid crystalcomposition of claim 39 wherein X or Z is a —N(CH₃)₂ group in theformula of the liquid crystal compound which exhibits negativebirefringence.
 41. The liquid crystal composition of claim 39 whereinone of X or Z is an electron donor group and the other of X or Z is anelectron acceptor group.
 42. The liquid crystal composition of claim 23wherein rings E, F, G, H, I and J are phenyl rings, b₁ and b₂ are 1, c₁and c₂ are 0, and B₁ and B₂ are —CO₂— in the formula of the liquidcrystal compound which exhibits negative birefringence.
 43. The liquidcrystal composition of claim 42 wherein d₁, d₂, e₁ and e₂ are all 1 andD₁, D₂, E₁ and E₂ are all —O— in the formula of the liquid crystalcompound which exhibits negative birefringence.
 44. The liquid crystalcomposition of claim 43 wherein R¹ and R² are both chiral non-racemicalkyl groups in the formula of the liquid crystal compound whichexhibits negative birefringence.
 45. The liquid crystal composition ofclaim 44 wherein R³ and R⁴ are alkene groups in the formula of theliquid crystal compound which exhibits negative birefringence.
 46. Theliquid crystal composition of claim 45 wherein R³ and R⁴ are dienes inthe formula of the liquid crystal compound which exhibits negativebirefringence.
 47. The liquid crystal composition of claim 46 wherein R³and R⁴ are both trans, trans —(CH₂)₈—CH═CH—CH₂—CH═CH—C₅H₁₁ groups in theformula of the liquid crystal compound which exhibits negativebirefringence.
 48. The liquid crystal composition of claim 47 wherein R¹and R² are both chiral non-racemic —(CH₃)CH—C₆H₁₃ groups in the formulaof the liquid crystal compound which exhibits negative birefringence.49. The liquid crystal composition of claim 48 wherein Y₁-Y₄ arehydrogens in the formula of the liquid crystal compound which exhibitsnegative birefringence.
 50. The liquid crystal composition of claim 49wherein one of X or Z is NO₂ and the other of X or Z is NR′R⁵, where R′is a small alkyl having 1 to about 3 carbon atom and R⁵ is an alkylgroup in the formula of the liquid crystal compound which exhibitsnegative birefringence.
 51. The liquid crystal composition of claim 50wherein one of X or Z is a —N(CH₃)₂ group.
 52. The liquid crystalcomposition of claim 23 wherein one of X or Z is an electron donor groupand the other of X or Z is an electron acceptor group.